GIANO-preslit: user manual, description and performances
Contents
1. GIANO preslit user manual description and performances 15 Sep 2013 Page 13 of 43 ND 0 2 95 ND 1 0 895 ND 0 3 255 ND 2 0 1055 ND 0 4 415 ND 3 0 1215 ND 0 5 575 ND 4 0 1375 Tab 3 Neutral Density values TS DIFF LIMIT S 0 0008 0 0008 DEG TS 0 0000 0 0000 DEC TS_ 0 0008 0 0000 DEC TS 0 0000 0 0008 DEG TS 0 0008 0 0000 DEG 1 0 T T T T O9 4 08 E o ae 4 I bep a D5 H 4 Q Y pa l o3 _ Q gt azb 4 ol 0a I I I L I a 24 48 72 96 120 240 SPATIAL FREQUENCY IN CYCLES PER MM POLYCHROMATIC DIFFRACTION MTF GIANO OPTICS VS 9 HR MON SEP 9 2013 DATA FOR 9000 TO 1 1000 um SURFACE IMAGE TNG_OIG_VER6_GUIDER_TZZ_ ZMX CONFIGURATION 1 OF 18 We are intentioned to modify the Bandpass Filter to increase the throughput on the guider especially for giant red stars This can be easily done changing the filters in particular the FEL one Fig 11 MTF of the guider system optics that are mounted on a standard Thorlabs mechanical fixed mount GIANO preslit user manual description and performances 15 Sep 2013 Page 14 of 43 Light path description of the Fiber Viewer camera The Fiber Viewer is based on the same CCD camera used by the Guider On the optical beam in the Giano Preslit Box an IR LED can be inserted and switched on varying the intensity The light is partially collected into the two ZBLAN fibers and re2. that we remember in Giano is placed quasi horizontal Lens L1 and L2 are the same matching lenses used the last year for the preliminary test of Giano and form a refocusing relay lens to well match the outcoming f number of the preslit system with the nominal incoming f number of the cold optics that if f 9 5 the nominal f is in fact f 10 and the diameter of the two foci on the slit is 175 micron with respect to the slit dimension of 150 micron in the maximum resolving power position The slit is mounted on a rotary stage that has several slits and other support alignment device but actually this wheel is fixed on the 150 micron slit and the motor driver is kept switched off permanently DON T switch on this motor no movement of the slit rotary wheel is permitted without the approval of Arcetri team GIANO preslit user manual description and performances 15 Sep 2013 Page 25 of 43 4 1 cold slit D o Fi D 175pm E ood stop o max f3 5 O noslicer slicer Giano window L1 L2 with slicer P7 a P 4 5 Calib star P6 P5 with slicer Fig 22 Schematic representation of the Fiber Spectrometer interface assembled into the Preslit Giano Box P4 P7 are Parabolic mirrors FM8 is the rotator folding mirror SLC the sclicer In the top right red box the matching between the slit and the foci is represented in case the slicer is used or not used In Fig 23 the 3D desig
3. 2 257 1015 5280 35 2 192 735 4050 36 2 131 520 3000 37 2 074 340 2100 11700 38 2 019 225 1440 8490 39 1 967 146 980 6070 40 1 918 92 665 4195 41 1 871 435 2950 42 1 827 295 2090 10050 43 1 784 202 1505 7490 44 1 743 135 1050 5490 45 1 705 125 3940 46 1 668 501 2895 47 1 632 340 1995 11550 48 1 598 230 1450 6330 49 1 565 155 1040 4705 50 1 534 110 745 3500 12450 51 1 504 520 2495 9595 52 1 475 380 1900 7205 53 1 447 270 1370 5395 54 1 420 1002 4250 55 1 394 740 3195 56 1 369 2400 57 1 345 1870 58 1 322 1410 59 1 299 1080 60 1 278 830 61 1 257 630 Tab 8 Measured fluxes with GIANO spectrometer looking directly at a black body source The photons flux expected from the calibration source at a given temperature T is given by D pix 2c A exp he AkT 1 8 Apix AApix Qpix photons s pix where Epb 0 97 emissivity of the calibration source Apix 3 24 10 cm area of one pixel pixel size 18um Qpix 27 1 cos Opix 0 061 sr solid angle of light cone illuminating a pixel The spectrometer absolute efficiency is ratio between the measured flux of photo electrons and pix The results are summarized in Fig 34 The peak values of efficiency occur in the K band and are about 22 this value is very close to
4. RS components 689 215 5 The OIG Box can be run on the two vertical micrometer So doing the box can be removed by its support and alignment structure The mounting procedure is the same of the dismount one but from the last point to the first one great attention MUST be paid to the IMPORTANT NOTE 1 few rows above GIANO preslit user manual description and performances 15 Sep 2013 Page 22 of 43 3 6 Electronic plan In the following figure the electronic cabling is sketched TNG Nasmith OlG Lantronics Portserver ZBLAN calio n her Powersupplies box O Qo CakLamp ZBLAN double fiber i shaker OIG bench PI motor l O Mcarsin Filter Whee Dstep calibration box Electronic box 25 pin cable Pl Motor cable 15 pin Giano Bench Fig 20 Schematic representation of the electronic cabling J The electronic Preslit Rackmount contains all the electronics needed for the preslit It is composed by PC Xill Lantronix Ethernet RS232 portserver Calibration box Ne Uranium driver lamp Electronic box Power supplies box AMOAW YS Below a spare volume for future devices GIANO preslit user manual description and performances 15 Sep 2013 Page 23 of 43 4 The fibers spectrometer interface The interface between the science fiber and Giano spectrometer is realized in the Preslit Giano Box visible in Fig 17 and Fig 23 Inventor 3D desi
5. micron 11 4 2 47 micron GIANO preslit user manual description and performances 15 Sep 2013 Page 29 of 43 The second one is the slicer that can be aligned using the six axes regulations of the commercial stage by Thorlabs on which it is mounted and the third one is the output fiber connectors that is a custom device as visible in Fig 27 ine I TETE Fig 27 The Fiber out custom connector and angular regulation Using the fine fiber angle regulation it is possible to fine align the two foci on the slit in a range of 3 5 after this using the six axes regulation of the slicer it is possible to tune position and forms of the four half moons generated by the slicer To unlock the fiber regulation mechanism you have to unlock before the Screw 1 and the Screw 2 After this you can rotate of some degrees the fiber end of the science fiber 4 3 The Image Slicer The image slicer is a particular optical components that is able to divide an input beam into two or more than two slices and to reassemble the single slice side by side in the output beam In Fig 28 a photo of the Image Slicer is shown where in red is represented the only input beam and in green the two sliced beams Fig 28 Photos if the Imge Slicer prisms In red the input in green the output The idea of the slicer is to find something to recover the lost light that falls out of the slit as visible in the side figure The use
6. the 23 measured in Arcetri before shipping to the TNG The decrease of efficiencies toward the shorter wavelengths is caused by the intrinsic drop of quantum efficiency of the replacement detector which was sent to us in 2011 after the major failure of the original science grade array GIANO preslit user manual description and performances 15 Sep 2013 Page 38 of 43 Efficiency of doublet window spectrometer Jul 22 2013 Giano doublet looking at black body 0 25 0 20 S gt On p E T 108 C T 150 C T 200 c T 250 C A T 300 C Z T 350 C li i 1 2 1 3 14 15 16 17 18 19 20 2 1 2 2 2 3 2 Wavelength um Fig 34 Absolute efficiencies of the GIANO spectrometer without fibers interfaces A GIANO preslit user manual description and performances 15 Sep 2013 Page 39 of 43 5 2 The end to end absolute efficiency of GIANO The measurements were performed during the night of 2013 July 30 using the same black body source described in the previous section The measurement setup is shown in Fig 35 Fiber GIANO interface including image slicer GIANO spectrometer OIG fiber interface D 60mm fit science fiber Black body aperture 660mm Fig 35 Schematic layout of the setup used to measure the end to end absolute efficiency of GIANO The spectrometer was at operative condit
7. the calibration source stabilized at T 150 C Data at other temperatures were not taken because of the long time necessary to change and stabilize the black body temperature The photo electrons flux from the detector was determined as the flux per spectral resolution element 2 pixels measured on the extracted 1D spectrum which includes all the signals from the two fibers The measured fluxes are summarized in Tab 9 the values can be transformed in flux of photo electrons using the conversion factor of GIANO array electronics 2 2 el ADU GIANO preslit user manual description and performances 15 Sep 2013 Page 40 of 43 Order x um Measured ADU per specu Tao element in 10s T 150 C 32 2 398 66900 33 2 325 53200 34 2 257 39600 35 2 192 30400 36 2 131 23000 37 2 074 16400 38 2 019 11200 39 1 967 7510 40 1 918 4840 41 1 871 3220 Tab 9 Measured fluxes with end to end GIANO system looking at a black body source The photons flux expected from the calibration source at a given temperature T is given by Dy fibe 2c L exp he AkT 1 Ebb Afb A Ofib photons s where Epb 0 97 emissivity of the calibration source AX M47 000 width of spectral resolution element Agp 5 8 107 cm projected area of the fibers at F 11 Orin 27 1 cos 0 5 11 0 0065 sr solid angle of F 11 light cone The end to end absolute efficiency is ratio between the measured flux of pho
8. the optical quality of the foci themselves The stage is based on a commercial Physik Instruments device M 116 and has the appropriate angular resolution to realize a scan procedure of the slit at the purpose to maximize the signal on the Giano s detector The whole mechanism is mounted on a mechanical support structure that can be manually rotated using two micrometer screws The vertical rotary axis of this regulation is positioned on the center of FM8 within 0 2 mm error This regulation is necessary to the horizontal fine positioning of the foci in the Giano cold slit while using the external box micrometers you can roughly adjust the horizontal position of the foci by tilting and translating the whole Preslit Giano Box The translation rate of the foci with respect to the rotating angle of FM8 is 90 micron arcmin being the dimension of the slit the following S075 1 120 x 0 140 mm Actually inserted S050 1 120 x 0 093 mm so to cover the whole height of the S075 slit you need to rotate the M 116 of 1 6 arcmin It can be done easily with great resolution using the PI stage e the minimum incremental motion of the stage is 50 microrad 10 31 arcsec e unidirectional repeatability is 12 microrad 2 50 arcsec The slit centering mechanism is one of the three devices that can move the image of the focus The Giano Detector pixel size is 18x18 micron Each pixel on the input cold slit has a nominal dimension of 18
9. the telescope is collimated and re imaged at the fiber F 4 9 focus using two off axis parabolae and two bending mirrors The output F 4 9 beam has a diffraction limit optical quality and is pseudo telecentric nominally the exit pupil in Zemax design is located 151 mm far from the focus and has a diameter of 31 mm but the chief ray angle for a field of 2 arcsec in sky far from on axis one is only 3 5 arcmin This comport a lateral shift of the pupil of 0 017 A dichroic beam splitter on the collimated beam reflects the blue lt 850nm light to the guider An image of the TNG pupil is accessible before the dichroic as visible in the photo on this side taken during daytime placing a piece of paper in front of the dichroic The dome was opened during the test so the primary mirror and spiders are well visible f 11 TNG focus P1 f 4 9 fiber focus FM1 30 LAYOUT GIANG OPTICS V5 9 CHR MON SEP 9 2013 TNG_OTG_VER6_FIGERIN_T22_1 2Mx CONFIGURATION 1 OF 1 Fig 7 Zemax optical design of the downstream mode P1 and P2 are commercial parabolas BS is the dichroic beamsplitter FM are folding mirrors File TNG_oig ver6_fiberin_tzz_1 zmx In the Fig 7 is shown the design of the downstream mode The first off axis parabola P1 is placed 152 4 mm after the f 11 TNG focus so the output beam is collimated by the P1 parabolic mirror having an Effective Focal Length EFL of 152 40 mm with an error of 1 The beam is f
10. used to determine the center and FWHM of the I a 6 function The results always indicated that the star was correctly centered on the fiber and that the FWHM was compatible with the seeing which noticeably was in most cases much better than 1 the sky projected diameter of a fiber GIANO preslit user manual description and performances 15 Sep 2013 Page 42 of 43 In parallel with the low throughput of the stellar spectra we also noticed that the flux of the airglow emission lines was significantly lower than expected for typical values of sky emission However a reliable estimate of efficiency could not be derived because the emission of the airglow may significantly vary on time scales of several hours Nonetheless we could perform a direct measurement of the relative efficiency of GIANO with and without the telescope This test consisted of dismounting the telescope OIG interface and taking frames of the diffuse sky emission airglow lines thermal background in the following set ups 1 Fiber pointing directly to the sky 2 Fiber connected to the OIG interface with the interface pointing the interface directly to the sky 3 OIG interface mounted back on the telescope with the telescope pointing at the sky at the same azimuth and elevation used for previous measurements Two frames of 5 minutes were taken in each set up The complete sequence was completed in about 45 minutes The time variation of the airglow e
11. 0 1030 1040 1050 1060 2 Position amp Fig 37 Spectrum of a sky airglow line taken with different configurations see text for details Image testi_direct Rov 1 4 black fiber direct red fiber 0IG_int A blue fiber 0IG_int TNG Thermal background along slit a m hf gt a Hl g 3 a g 8 ibers positions ke nh N F 3 240 260 280 300 Position Fig 38 Variation of thermal background along the slit measured with different configurations see text for details
12. 202 ozzi arcetnasiro it email ANS __ parallelism between fiber axis lt 5 arcmin 1 Fig 1 Design of the custom fiber optics patch cord Core diameter of each fiber is 84 micron 1 arcsec in sky Distance between centers is 250 micron 3 arcsec in sky The two fiber termination are placed vertically with respect to the Preslit OIG box optical bench plane this will be important for the definition of the observing modes as described in chapter 3 2 Observing modes It is important to say that the core dimension is 1 arcsec in sky and that the distance between centers is 3 arcsec in sky GIANO preslit user manual description and performances 15 Sep 2013 Page 6 of 43 Fig 2 Optics of the Preslit OIG box 3 1 Opto mechanical design Description of the board optical parts size and weight are below reported The OIG box is based on a commercial 60X30 cm aluminum optical bench by Thorlabs onto which the optics are positioned as visible in Fig 3 The opto mechanical design is based on commercial elements including in particular three off axis parabolic mirrors which only recently became available as standard off the shelf optical elements In Fig 4 the alignment micrometers are visible OIG interface P1 P3 BF Fig 3 Inventor design of the Preslit OIG box FM are Folding plane Mirrors P are parabolic mirrors BS is the dichroic Beam Splitter ND the neutral Density sector w
13. 4 Detailed view of the D mirror placed on the f 11 TNG focus Mirrors are vertically mounted and the shape of these mirrors is like a D where the straight side is very well worked to generate a knife Two of these mirrors have been mounted on the same GIANO preslit user manual description and performances 15 Sep 2013 Page 16 of 43 mechanical mount using Millbond optical glue the two parallel sides form a slit of about one millimeter located at the nominal f 11 TNG focus The tilt regulations of the mechanical mount on which the D mirrors are placed are useful to align the outgoing calibration beam from lens L1 to be overlapped to the f 11 TNG telescope chief ray Fig 15 The two D mirrors are glued on an iron ring to take them in position one with respect the other Changing the value of M 111 linear stage position it is possible to have the following OMs 1 M 111 0 mm home position name CC gt 1 2 calib The Light from sky is blocked by the back surface of the D shape mirrors In this position the light from calibration input can be reflected by the bottom D shape mirror to the outgoing fibers and the guider along the input optical axis of the Preslit OIG box 2 M 111 1 7 mm position name CB gt star fiber down calib fiber up The bottom fiber is fed by the light from sky while the top fiber is optically conjugated to the calibration beam It is important to remember that the two parabolas M1 and M2
14. 7 22 mm the incoming beams from the two fibers are approximately f 4 9 The collimated beam is refocused by P5 off axis Parabolic Mirror off axis angle of 15 and EFL 654 99 mm The generated focused beam has an f equal to GIANO preslit user manual description and performances 15 Sep 2013 Page 24 of 43 120 The necessity to have a so big f number is related to the difficulties to build an image slicer of small dimensions with a so big f number we have the images of the two fibers equal to 2 04 mm being their real core diameter of 85 micron and the focal ratio of P5 and P4 of 24 and their center to center distance of 6 0 mm The beam is collected by P6 15 off axis parabolic mirror EFL 367 7 mm that collimates the beam again The last parabolic mirror P7 generates the correct f number in the correct position before entering in the matching lenses L1 L2 placed near the input window of Giano Cryostat P7 has an off axis angle of 30 and an EFL 54 45 mm it generates an f 16 beam in which focus we find an image of the two sliced cores of the Science Fiber Nominal diameter of the focus is 280 micron This auxiliary focus is very useful to check quality beam before entering the Giano Cryostat After this f 16 focus the beam is folded by FM8 which center is nominally placed on the axis of the cold stop of Giano This mirror is placed on a rotator stage to permit the alignment of the focus with respect to the slit
15. FIBERIN_TZZ_1 ZMX WAVELEN CONFIGURATION OF 1 The following table shows the scale factor of the different foci present in Preslit OIG Box Scale Focus Position f number micron arsec sky TNG focus on OIG flange 11 187 0 Fiber In on ZBLAN fibers 4 9 83 4 CCD Guider plane 4 9 83 4 Tab 2 Focus scale factor for the Preslit OIG box The magnification factor from f 11 TNG focus to f 4 9 Fiber focus is 2 24 GIANO preslit user manual description and performances 15 Sep 2013 Page 11 of 43 Light path description in the calibration mode The calibration mode optical design is represented in Fig 9 A fiber optics of 400 micron core diameter in ZBLAN feeds the Preslit OIG box the calibration NE U and Halogen lamps are in the box located into the rackmount placed on the Nasmity A platform The light is refocused by L1 commercial CaF singlet of 15 mm focal length on the f 11 nominal position of the TNG focus where a D shape mirror is located and can be easily positioned using a remote controlled motor linear stage M111 of MICOS PI Then the light follows the same optical path of the natural star and is focused on the fiber input terminations DM PI f 4 8 fiber focus bai i c TRI 30 LAYOUT MON SEP 9 2013 WG DIC VERG CALIBRATION ON FIBERS_T22_1 ZHX CONFIGURATION I OF I Fig 9 Zemax optical design for the Calibration mode P1 and P2 are commercial parabola
16. INAF OSSERVATORIO ASTROFISICO DI ARCETRI TECHNICAL DOCUMENT FOR GIANO preslit user manual description and performances 15 September 2013 Ver 1 Name Affiliation Signature Ernesto Oliva INAF Arcetri Andrea Tozzi INAF Arcetri Marcella Iuzzolino INAF Arcetri Livia Origlia INAF Bologna GIANO preslit user manual description and performances 15 Sep 2013 Page 2 of 43 Modification Record Version Date Author Section Paragraph Reason Remarks affected 1 i5 3ep2013 E Olivaetal all Bust releaseior ine document GIANO preslit user manual description and performances 15 Sep 2013 Page 3 of 43 Content COMUGIE sis ccascadsashauecd steseucessuietcacknaesinteboniadtatesssckanmesudesousiuddeued ila aaa 3 VAI ESE RE RIE PERI 4 2 Intioducetoni a i alec cbs cactes caste Lessnes Scacects sted sents laze ssas o oe oeer isio eaethudecthvccsssnedsendocats 4 3 The fibers lele scope Interfate ca sciare 5 3 1 Opto mechanical desigri rcr ai Asean 6 Light path description in the downstream working Mode 9 Light path description in the calibration mode criari lalla 11 Light path description of the guider camera uia lara 12 Light path description of the Fiber Viewer camera alia 14 3 25 Observing modes iure a a a a aa aaia 15 3 3 Gian s interfatesdestapion alessia 17 3 4 Bill Or Optical Materia
17. Input N2 plant Standard cryogenic tube Giano cryostat platform i Fi beam Light from tertiary mirror Preslit OIG Nasmyth A M25X1 tap is provided side derotator Tab 4 Giano s Instrumente interface list Colors are referred to Fig 5 Fig 17 Locations of the Giano s interfaces with TNG are shown GIANO preslit user manual description and performances 15 Sep 2013 Page 19 of 43 3 4 Bill Of Optical Material of OIG box In the following Table the bill of material of the optical components for the Preslit OIG Box is listed Acronym Manufacturer Type model Description notes 1 Silver EFL 152 4 mm PI Thorlabs ee protected Off axis angle 90 1 parabola same of Edmund 63196 1 gold P2 Edmund 63 193 protected Epo hh Off axis angle 60 parabola 1 gold E P3 Edmund 63 193 protected PESONA aie 3 Off axis angle 60 parabola Pecchioli 2 Infrasil Coating Tafelmeier BS Research Custom 302 coated X PELPFI 1 surf 4 Tafelmeier ee AR 2nd surf FM1 FM2 1 Silver Long pass i BF Thorlabs FEL 750 filter short Mounted in series on the 6 FES 950 same mechanical support pass filter ND Thorlabs NDGsi00s 4 PeP vanable 7 grey filters LI Thorlabs LB5766 PE 9 singlet lens Thorlabs D shape gold Assembled by DM Pecchioli Res PEDO wer mirror so Calibration l ABLAN SMA custom IR Photonics Custom core diam f 11 Fiber c
18. M4 FM8 are plane Folding Mirrors L1 L2 custom Lenses M116 a rotational stage MT a motor to control the LED position and SLC is the Image SLiCer The procedure of dismount remount of this box is the same of the OIG one and it is described in section 4 7 Fig 24 Alignment details of the Preslit GIANO box External micrometers are visible and GIANO preslit user manual description and performances 15 Sep 2013 Page 27 of 43 for each ones the correct nominal position is given in Tab 6 FM4 30 LAYOUT TWO 9 DEGRE E PARABOLAS WED SEP 11 2013 TNG_FIBER_OUT_VERS_2BIS ZMX CONFIGURATION OF I Fig 25 Zemax optical design for the Preslit Giano Box P are commercial parabolas File TNG_fiber OUT _ver5_2bis zmx GIANO preslit user manual description and performances 15 Sep 2013 Page 28 of 43 4 2 Slit centering mechanism The slit center mechanism visible in Fig 26 is based on a commercial rotary stage PI M116 that can control the vertical tilt angle of the folding mirror FM8 you find before L1 L2 optical system This plane mirror is nominally positioned vertically with respect to the optical bench and has its center located on the mechanical axis of the cold stop of Giano E Fig 26 The slit centering mechanism Because of the big field of view of L1 L2 reimaging system the vertical position of the f 10 foci can be changed without affecting
19. aches the Preslit OIG box using the same fibers normally used for the scientific measures on the sky The outgoing light from these two fibers is collimated by P2 parabolic mirror on the FM2 folding mirror Than is partially reflected by the Beam Splitter BS and totally reflected back again from FM3 folding mirror This mirror is normally covered by a black stop placed in front of it but this cover can be remotely controlled and removed The light from FM3 passes through the beam splitter BS and follows the same optical path of the incoming light from star normally reflected by the dichroic beam Splitter BS On Finger Lake CCD FLI CCD an image of the two fibers is generated on the CCD Guider simultaneously or not with the scientific target FLI CCD Fiber outs _ 30 LAYOUT TWO 99 DEGREE PARABOLAS MON SEP 9 2813 TNG OIG VERG FIBER VIEWER TZZ_I ZMX CONFIGURATION OF Fig 12 Zemax optical design for the Fiber Viewer branch P2 and P3 are commercial identical parabolas BS is the dichroic beamsplitter FM3 is a folding mirror ND is a neutral density filter wheel BF is a passband filter File TNG_oig ver6 fiber viewer_tzz_1 zmx The image of the two fibers is reimaged by the two identical off axis parabolas P3 and P2 on the CCD guider and so the magnification factor is equal to one The position of the two fiber images can be recorded and that coordinates on the CCD F1 x1 y1 and F2 x2 y2 will represent t
20. d spectrometers S075 slit without slicer in this case the focus is again 175 micron and the slit 140 micron We reduce the lost light but so doing we are limited by the background noise due to the bigger dimension of the slit In fact the detector looks to a bigger field of view around the image of the two fibers and this bigger FOV looks at hot material With respect to the use of S050 slit the background if 1 5 times more S050 slit with slicer the focus diameter if 175 micron again but because of the slicer we actually have four half moons with a height of 88 micron The slit is 93 micron so nominally it is possible to use this configuration but it leads to a challenging alignment A slightly rotation angle error in the positioning of fiber head sends the half moons out of the slit losing the image S075 slit with slicer in this case we have not round foci again but two couples of semicircles see Fig 29 one for each fiber The height of the four semicircles is half a focus diameter that it means 88 micron with respect to the slit height of 140 micron In this case we don t lost light in the matching the alignment is simpler than case 3 but we have again a factor 1 5 of background noise more that using S050 slit This is the configuration used for the Commissioning in July 2013 It is interesting to point out that using the image slicer we don t need the slit by a point of view of spectrograph resolution but it con
21. e telescope As a consequence Giano is fed via special fibers with extended transmission to the infrared wavelengths which are interfaced to the telescope at the ex OIG focus The interface is mounted on a quasi gravity invariant structure consisting of a horizontal bench fixed to a vertical bearing attached to the ex OIG flange At first the fiber telescope interface of GIANO was designed with minimal size resulting in a non easily adjustable matching After the 2012 commissioning a new interface has been introduced the new preslit system is composed by two different optical benches one mounted on the OIG Telescope interface and the other mounted directly on one side of the Giano Cryostat They have been realized mainly using commercial components in particular for the optomechanical devices this because of the short time used for the assembling This system has some new features with respect to the previous one PRESLIT OIG BOX 1 a full controlled telescope s optical axis fiber s axis alignment thanks to the available visible pupil check the adjustable optical components inside the OIG board and the possibility to align the whole OIG box using seven external micrometers realizing a full 3D alignment system 2 The possibility to look at the fibers position on the guider camera This is the upstream mode that is referred to the light going from a calibration source to the guider camera through the fibers in order to check the fiber al
22. e useful for many operations 1 16 beam is positioned after the image slicer So it is a very useful point to look at the image of the foci before entering Giano s cryostat It permits the fine alignment of the slicer and of the two science fiber 2 it can be used to measure the FRD of the science camera 3 it can be used to well align the telescope to the incoming fiber in the OIG box We currently use Giano s eschellogramme acquisition to verify the well fiber matching after having aligned the telescope using the FLI camera guider on the nominal position as registered by the fiber viewer See Fiber Viewer Modality in the software document If the light intensity is not maximized the telescope can be moved to maximize it Using the new auxiliary CMOS camera as a photon counter we gain at least a factor of 10 in time with respect to the actual procedure based on the eschellogramme In Fig 31 the Star centering system is shown It is based on an Ethernet CMOS CAMERA IDS 5242LE NIR and on a commercial linear stage LS 40 25 mm travel range by Physik Instrumente Micos controlled by a Pollux Driver via RS 232 After the measurement or optimization procedure the camera can be removed from the beam using the linear stage CMOS camera and a linear stage The red dashed arrow indicates the direction of sliding GIANO preslit user manual description and performances 15 Sep 2013 Page 34 of 43 4 6 Bi
23. generate an inverting optical system magnification from focus is 0 44 so the top fibers looks at the bottom f 11 focus 3 M 111 2 7 mm position name AC gt star fiber up calib fiber down The top fiber is fed by the light from sky while the bottom fiber is optically conjugated to the calibration beam 4 M 111 15 mm position name AB gt 1 2 sky The D shape mirrors are placed in the bottom as far as possible from the mechanical axis of the input hole The whole sky is visible by the guider as already said the nominal FOV in this condition is 2X2 arcmin but it is partially vignetted by the mechanical mount that supports the D shape mirrors GIANO preslit user manual description and performances 15 Sep 2013 Page 17 of 43 3 3 Giano s interfaces description In the following figure Fig 16 it is represented the general Giano spectrometer interface and the internal cabling scheme All the interfaces with TNG are represented and are listed with letters a b h i and they are of different types electrical blue and yellow gas grey and brown and light red TNG 2013 Nasmyth A side wall f e d c a3 b a2 al UPS out gas OutN2f Input Ether 1 UPS2 i UPS1 220 Vac rotative pump gastt1 dry air 380 Vac 220vac Ether 2 PRESLIT Giano Box GIANO CRYOSTAT PLC CRIOGENIC 18 elec cables RACK Detector 8 opt fiber_____ electronics Cres do Lil ici de Libers er Serer ert Per
24. gn The box has the following dimensions 606 X 456 X 140 mm and has a mass of 25 Kg The whole system composed by the box itself and the support structure is attached to the Giano input flange by 12 M6 screws The total mass is 35 Kg II STA Fig 21 The inner of the Preslit Giano Box 4 1 Opto mechanical design The 3D optomechanical design in visible in Fig 23 and the Zemax design in Fig 25 The red beam is the backup optical beam and is not described in the present document because it is currently not used it is an optical path that can be considered in case that the Image Slicer is not adopted In fact the more complexity of the operative optical beam in green in figure is related only to the introduction of this Image Slicer SLC The starting point of the design of the Fiber Spectrometer interface is the incoming minimum f number that Giano Cryogenic optics accept This value is mechanically defined by the ratio of the distance cold stop cold slit and the diameter of the cold stop itself nominally it is f 9 5 This choice comes from the hard definition of the fiber s f number due to the fiber focal ratio degradation FRD as used quality parameter for fiber The FRD varies with the incoming f number and because of the polishing procedure of each single fiber The output beam coming from the Preslit OIG Box via the Science fibers optic is collimated by the first Parabolic Mirror P4 with 30 off axis angle and EFL 2
25. he correct position in which to align the scientific target under investigation during scientific observation This is true provided that the folding mirror FM3 has not changed position in the course of time otherwise a recalibration procedure will be necessary and an offset to the two CCD pixel coordinate F1 and F2 will be necessary GIANO preslit user manual description and performances 15 Sep 2013 Page 15 of 43 TS DIFF LIMIT TS 1250 0 0000 M TS 0 0000 2 0000 MM S 0 0000 0 1250 MM TS 0 1250 0 0000 MM TS 0 0000 1250 MM 1 0 T T T T MODULUS OF THE OTF 0 0 i li i li i 4 a 19 38 57 76 95 114 133 152 101 190 SPATIAL FREQUENCY IN CYCLES PER MM POLYCHROMATIC DIFFRACTION MTF TWO 90 DEGREE PARABOLAS MON SEP 9 2813 DATA FOR 8 9000 TO 1 1000 um SURFACE IMAGE TNG_OIG_VER6_FIBER VIEWER_TZZ_1 ZMX CONFIGURATION 1 OF 1 Fig 13 MTF of the Fiber Viewer system optics 3 2 Observing modes According to what previously said and referring to the figures Fig 3 Fig 5 Fig 6 we now illustrate the Observing Modes OM The inputs of the two optical ZBLAN fibers are vertically disposed in the Preslit OIG box This fact permits to operate in different observation modality only moving the translation stage M 111 on which the two D shape mirrors are mounted as visible in the detailed design photo of Fig 14 and if Fig 15 Fig 1
26. heel DM the D shape Mirror L1 is a lens BF a Pass Band filter In dashed red arrow the input of the fiber calibration light in green the science output fiber GIANO preslit user manual description and performances 15 Sep 2013 Page 7 of 43 F ig 4 Alignment details of the Preslit OIG box External micrometers are visible and for each ones the correct nominal position is given in Tab 1 The positions of the micrometers are the following Front Front Front i i Back o Description Vertical Orizzontal Focus Left Right Vert Left Right Acronym FY FO FF BOL BOR BVL BVR Value 11 43 6 10 7 21 6 83 19 12 11 50 11 50 mm Tab 1 Micrometer positions of the Preslit OIG Box on 2 Aug 2013 Position and identification names of the micrometers are reported in Fig 4 The mounted size of the Preslit OIG box are 600mm x 300mm x 120 mm and its weigh is 20kg this box can be easily removed and it is the part of the system that will be aligned on the telescope f 11 beam using the micrometers The total weight of the interface including the flange adapter and support system is about 39kg In Fig 5 and Fig 6 are represented the conceptual designs of the Preslit OIG Box The optical design is composed by at least four optical designs described in the following paragraphs This because of the different operating modality we have for this board GIANO preslit user ma
27. ignment with respect to the telescope s axis PRESLIT GIANO BOX 1 a full controlled Giano optical bench fiber s axis alignment thanks to the adjustable optical components inside the Giano side box board and the possibility to align the whole box using seven external micrometers realizing a full 3D alignment system 2 The possibility to increase the efficiency using a slicer prism 3 The possibility to look at an intermediate focus before the beam enters in the cryostat GIANO preslit user manual description and performances 15 Sep 2013 Page 5 of 43 3 The fibers telescope interface The fiber telescope interface is realized by the Preslit OIG Box described in the following paragraphs First of all it is important to remember that the two Preslit boxes are optically connected by a couple of fibers optics assembled as shown in the following design in the same SMA connector IMPORTANT NOTE according to our measurements it is crucial do not modify the fiber cladding Fiber acrylate buffer diameter has the appropriate diameter to permit placing side by side the two fibers SMA fiber connector for example Thorlabs 10510A ZBLAN fiber optics 85 micron core 247 micron external diameter gre Polished surface of SMA connector Yellow core diameter 85 micron Orange cladding diameter 125 micron Blu buffer diameter 247 micron Glue Ferrule hole 250 micron ZBLAN fibers Fax 39 055 2752
28. ions with all the cryogenic parts stabilized at a temperature of about 80K As cold slit we used S075 whose width and length 0 14 x 1 12 mm projects onto 3 x 24 pixels of the detector This slit is larger than the image of the fibers It is used as field stop to minimize the thermal background at the longer wavelengths The spectral resolution of the data is determined by the width of the image of the fiber produced by the image slicer see below The light was taken to the spectrometer through all the sub systems which constitute the interface between GIANO and the telescope In particular the measurement included the same fiber and image scrambler used for scientific observations The black body source whose aperture has a diameter of 60mm was positioned at 660mm from the focus of the OIG fiber interface Thus the interface was illuminated with a beam aperture of F 11 identical to that of the telescope In this configuration the spectrometer slit is the image of the fibers produced by the fiber interfaces The image of two fibers de projected onto the entrance F 11 focus of the OIG fiber interface consists of 4 half circles with radius 0 096 mm aligned along the direction perpendicular to the dispersion Therefore the total area illuminated by the black body at F 11 is 0 058 mm The spectral resolution of the data is determined by the slit width of the fibers image It amounts to R A AA 47 000 The measurements were performed with
29. l of OIG boxe 19 3 5 Dismounting Mounting procedure i 20 3 6 Eroe era 22 4 The fibers spectrometer interface 0 lt cecesscoocscoesssocesssoesssecsecsocssosensnsstecssscnonssenesseennssseass 23 4 1 Opio mechanical desigti cs rcehe steli 23 4 2 Slit centering mechanism 28 4 3 Pie lmassisliceeoa accennare 29 44 Fiber scramblerinechanism clara aaa 32 4 5 SS CLS STIS AND MECIanBRicli ille 39 4 6 Bill Of Optical Material of Preslit Giano DOX 34 4 7 Preslit GIANO box Dismount Mount Procedure iii 35 5 Measurements Of CHICIONCY nina rara 36 5 1 The absolute efficiency of the GIANO spectrometer 36 5 2 The end to end absolute efficiency of GIANO 39 DI Efficiencies with the telescope and looking directly at the Sky n 41 GIANO preslit user manual description and performances 15 Sep 2013 Page 4 of 43 1 Scope This document describes the new fibers interface of GIANO which was mounted and tested at the TNG telescope during the commissioning runs in 2013 It also includes the maintenance procedures and summarizes the results of the measurements of efficiencies performed during the same runs 2 Introduction In the first Giano commissioning on July 2012 the spectrograph was located in the TNG Nasmyth A and was positioned on the floor of the rotating building detached from th
30. ll Of Optical Material of Preslit Giano box In the following Table the bill of material of the optical components for the Preslit Giano Box is listed Acronym Manufacturer Type model Description notes 1 Silver EFL 27 22 mm P4 Edmund 63 192 protected Off axis angle 30 parabola 1 gold Off axis angle 15 parabola 1 gold B P6 Edmund 69 154 protected EFL a 331 0071001 Off axis angle 15 parabola 1 gold E Off axis angle 30 parabola Pecchioli Bowen SLC Custom Wallraven Image slicer Research prism protected lens CaF singlet L2 Gestione Silo custom lens Tab 7 Bill of material for the optical components for the Preslit OIG Box GIANO preslit user manual description and performances 15 Sep 2013 Page 35 of 43 4 7 Preslit GIANO box Dismount Mount Procedure Mechanical blocks P A 4 Fig 32 Figure shows the mechanical blocks to lock the Preslit GIANO box The Preslit Giano box can be dismounted and mounted on the mechanical support structure that is fixed to the entrance windows flange of giano s cryostat The alignment blocking system is completely the same as used for the OIG Box and described in section 3 5 here the mechanical blocks are at least the four shown in the figure 31 but we are intentioned to add other two ones Because of the critical alignment of the focus with respect to the incoming cold slit of Giano no dismounting procedu
31. mission was monitored using the individual frames one every 10 seconds which are stored by the non destructive read out procedure No significant variation was detected The results are summarized in Fig 37 and Fig 38 The first figure shows the extracted spectrum of a prominent airglow emission line The level spectrum with the OIG interface pointing at the sky is about 80 of that with the fiber alone This is in good agreement with the measured throughput of the optics system inside the OIG interface The measurements through the telescope instead are a factor of about 5 weaker than those with OIG alone The plots in Fig 38 show the variation of the flux seen by GIANO along the slit at 2 32um At this wavelength the GIANO cold slit sees a quite strong thermal background from the environment at ambient temperature The part of the slit looking in between the fibers sees a black body at ambient temperature The part of the slit looking at the fibers instead sees a lower thermal emission because the temperature and emissivity of the sky are much lower The decrease of flux is most evident in the data taken with the fiber looking directly to the sky as expected The measurements with the OIG interface looking at the sky are characterized a somewhat shallower decrease of flux roughly compatible with the emissivity of the optics inside the OIG interface The data taken through the telescope instead show very weak drops of flux at the fibers position
32. n of the Preslit Giano Box is shown You can find the optical devices already mentioned and something else MT is a stepper motor identical to that one used for the ND filter wheel in the OIG box and to that one used for the optical switch in the calibration unit box In this case it moves an IR LED that can be inserted into the optical collimated beam between P4 and P5 it is directed versus P4 and generates an f 5 beam that is focalized by P4 to the fiber ends This light is the used one by FLI CCD to locate the fiber positions in the OIG box Observation modality fiber viewer In Fig 24 the alignment micrometers are shown It is the same system used for OIG box and the positions of the micrometers are the following Front Front Front _ aoe Back a Description Vertical Orizzontal Focus Left Right Vert Left Right Acronym FV FO FF BOL BOR BVL BVR Value 17 00 1 15 4 00 20 50 5 15 17 50 16 75 mm Tab 6 Micrometer positions of the Preslit GIANO Box on 2 Aug 2013 Position and identification names of the micrometers are reported in Fig 24 GIANO preslit user manual description and performances 15 Sep 2013 Page 26 of 43 Giano cryostat in siano c putflange Fiber from OIG box Fig 23 Inventor design of the Preslit Giano Box In red the backup optical path NOT USED and not described in the present document In green the used one P4 P7 are Parabolic Mirrors F
33. nual description and performances 15 Sep 2013 Page 8 of 43 DM P2 star Halogen FM2 solenoid FM3 Fig 5 Conceptual plot of the Preslit OIG box in the downstream modality Dashed lines represent motorized axis Fig 6 Conceptual plot of the Preslit OIG box in the upstream modality P3 is an identical off axis parabola of P2 In Fig 5 the observing configuration in which one fiber looks at the sky and the other looks at the calibration lamp is schematically shown In Fig 6 the Upstream modality is represented an Infrared LED is remotely switched on in the Preslit Giano Box and placed in front of the fibers using a motorized system This is Fiber Viewer modality and is described in Light path description of the Fiber Viewer camera paragraph In Fig 5 and Fig 6 the dashed lines represent the movable axis remotely controlled that are 1 The motor stage M 111 for the position regulation of the D shape mirrors located on f 11 TNG focus based on a Mercury PI commercial driver 2 The motor stage for the Neutral Density filter wheel based on a custom step motor driver 3 The solenoid to insert remove the light stop for the fiber viewer The Zemax designs for the different optical path are below listed and described GIANO preslit user manual description and performances 15 Sep 2013 Page 9 of 43 Light path description in the downstream working mode The F 11 beam from
34. ocus and necessary to change the observing mode P3 ND f 11 TNG focus BF BS 3D LAYOUT GIANO OPTICS MON SEP 9 2013 V5 9 THR TNG_DIG_VER6_GUIDER_TZZ_1 ZMX CONFIGURATION 1 OF 10 Fig 10 Zemax optical design for the Guider branch P1 and P3 are commercial parabolas BS is the dichroic beamsplitter FM ais a folding mirror ND is a neutral density filter wheel BF is a passband filter file TNG_oig ver6 guider _tzz_1 zmx After the Dichroic Beam Splitter there are positioned a BandPass filter BF and a multi position Neutral Density Wheel having the following ND values 0 1 0 2 0 3 0 4 0 5 0 6 1 0 2 0 3 0 and 4 0 The transmission can be calculated by T 10 The non perfectly parallelism of the two surfaces that compose the grey filters have been measured and it is negligible so the translating effect of the stars measured by the guider is not affected by the ND filter wheel and no look up table is necessary Before the ND filter wheel a Bandpass Filter BF is placed on the optical path It has been realized using two commercial filters of thorlabs cut on FEL 750 cut off FES 950 Neutral density values and their motor step positions are the following Neutral density name Motor step value Neutral density name Motor step value ND 0 1 1535 ND 0 6 135
35. of the slicer permits to rearrange the shape of the focus without changing the Lagrange Invariance recovering the lights that otherwise would be lost GIANO preslit user manual description and performances 15 Sep 2013 Page 30 of 43 In case of Giano spectrometer there are two main slits called S050 and S075 which dimensions with respect to the dimension of the core of the science fiber 85 micron are in one case too small and in the other a bit more thick No other change was possible because of the pixel size dimension of the IR detector equal to 18x18 micron that corresponds to 47x47 micron on input Cold Slit optical plane As visible in Fig 22 the core diameter of the two fibers is 85 micron that are reimaged on the Cold Stop with a magnification of 2 06 so the diameter of the image is 175 micron noslicer slicer Now we have to consider the dimension of the slit already mentioned in the previous paragraph S075 1 120 x 0 140 mm nominal collecting angle in sky of 0 75 arcsec amp Actually inserted S050 1 120 x 0 093 mm nominal collecting angle in sky of 0 50 arcsec The possible alignments fiber slit modes are four l S050 slit without slicer in this case we have a focus of 175 micron with respect to a slit of 93 micron that it means we lost approximately half light of the total transported by the fiber In this case the spectrometer works slit limited as normally happens in standar
36. olded and a pupil image is placed in the dichroic beam splitter So P1 realizes a real image of the primary mirror on the beam splitter The second off axis parabola P2 has an EFL of 67 74 mm with an error of 1 and generates and f 4 9 output beam focalized on the input fiber termination The scale of this focus is 83 4 micron arcsec in sky and the whole system is diffraction limited in the full wavelength range 900 2400 nm as shown in the following figure Fig 8 GIANO preslit user manual description and performances 15 Sep 2013 Page 10 of 43 TS DIFF LIMI TS 0 0000 0 0 TS 0 0000 DEG TS 0 0001 3 TS 0 0000 1 DEG S B B001 ppo DEG 10 T T T T T 09 H 4 ne H u jazi x o aL J u I Deb 4 u asp m a Y 0 4 H a 5 Qi eer 7 a gt azl B1 H LL Da L L L L i o 21 42 63 BY 105 126 ur 168 189 210 SPATIAL FREQUENCY IN CYCLES PER MM POLYCHROMATIC DIFFRACTION MTE GIANO OPTICS V5 9 HRI MON SEP 9 2013 DATA FOR 1 0000 TO 2 4800 um SURFACE IMAGE TNG_OIG_VER6_FIBERIN_TZZ_1 ZMXx CONFIGURATION 1 DF 1 Fig 8 MTF of the fiber in optical path De as n S x io N a HA a DI 4 0 ao a s i z amp iwi n ra le e APERTURE DIAMETER 2 0849 RAYS THROUGH 100 00 EDDTPRINT DIAGRAM CIANO OPTICS V5 9 HR MON SEP 9 2013 SU 24 RAY X M RAY Y M TNG_DIG_VER6_
37. onnectorized 85 micron Scientifi 1 ZBLAN eaten IR Photonics Custom core diam SMA connectorized 12 Fiber 400 micron Tab 5 Bill of material for the optical components for the Preslit OIG Box GIANO preslit user manual description and performances 15 Sep 2013 Page 20 of 43 3 5 Dismounting Mounting procedure The Preslit OIG Box is aligned on the f 11 TNG beam using the seven micrometers described above After this the mechanical blocks see Fig 18 can be inserted to avoid the possibility of accidental movements of the box itself especially during the rotation of the OIG flange Fig 18 Figure shows the mechanical block to lock the OIG box The dismount procedure of the OIG Box is the following 1 first of all it is necessary to remove the two mechanical blocks It is important to note that there is no need to move the micrometers from their original positions 2 it is necessary to open the cover of the OIG box removing the four corner screws on the top side wall 3 The OIG Box has six functional connections 4 electrical cables and 2 optical fibers that will be necessarily unplugged as shown in Fig 19 Four of these six connection are externally located and can be easily removed on the back side wall of the OIG Box But two of these connections the Science Fiber Optic and the PI M111 Motor Cable have the connectors located INTO the OIG box In Fig 19 their positions are pointed out by red triangle
38. r er ert rr er os nanranansannanannann 25 pin cable A Tozzi July 13 PRESLIT PRESLIT GIANO INSTRUMENTE INTERFACE 4 cables Hop wire FLIUSB icomm OIG box wrap FLI power 2 wir M111 motor PI Input N2 plant ND wheel 4 wir f 11 input beam Out Ne gas 2 solenoid 2 vir i a I i cl 8 h TNG Nasmyth A platform Fig 16 Giano general interface scheme electrical blue and yellow perimetric boxes gas grey brown and green boxes and light red The Giano instrumente internal cabling is represented too Below in the table the interfaces between Giano instruments and the TNG structure are listed In Fig 17 the photo shows the locations of the listed interfaces GIANO preslit user manual description and performances 15 Sep 2013 Page 18 of 43 Letter color Name Type Giano device TNG location f Cryogenic Nasmyth A al Ac power line 220 Vac two phases a wall a2 AC power line 380 Vac try phases Giano Cryostat el A Preslit Nasmyth A a3 AC power line 220 Vac two phases Rackmount wall Preslit Nasmyth A b Ethernet RJ45 connection fan aall Cryogenic Nasmyth A c Ethernet RJ45 connection Race noun wall d Input Dry air Silicon tube Giano Cryostat de A e Out line for N2 Metal tube Giano cryostat aee A f Out line pump Rotative pump jacket Giano cryostat ee 2 g Out line for N2 Metal tube Giano cryostat Ney platform Nasmyth A h
39. r mechanism is able to eliminate the Modal Noise that is usually present in an IR eschellogramme when a fiber optic is used to transport the telescope light to the spectrometer as discussed in the previous document of commissioning 2012 It is based on a series of rotating disks that operates a shacking movement to the external fiber jacket Because of the fragility of these ZBLAN fibers the minimum static radius of torsion for these fibers is 50 mm due to the dynamic way of use we have doubled this specification The scrambler is positioned on the Nasmyth A platform near the Giano cryostat the fibers from OIG box enters in the mechanism from the top side and exits to the bottom To insert the fibers in the scrambling mechanism it is not necessary to unplug it the top and bottom blocks have two screws that can be removed when you have to insert extract the fibers The fibers has to be passed in the central zone passing right left with respect to the wheel alternatively The power supply to the DC motor is guaranteed by an electric cable pin to pin DB25 coming from the Preslit Rackmount GIANO preslit user manual description and performances 15 Sep 2013 Page 33 of 43 4 5 Star centering mechanism In October 2013 we are intentioned to insert on the f 16 focus between P7 and folding mirror FM8 a definitive CMOS Camera as we used in July during the installation of the new Preslit This camera would b
40. ral resolution of the data is determined by the slit width and amounts to R A AX 47 000 thus each pixels sees a wavelength range AApix A 47 000 of the continuum emission from the calibration source The angular aperture of the light seen by the detector is defined by a cold stop positioned before the cold slit The semi angle of the cone is 0 8 0 equivalent to a focal ratio of F 3 6 Measurements were performed with the black body source stabilized at different temperatures namely 108 150 200 250 300 and 350 C For each temperature we used the data at a dozen of wavelengths corresponding to the centers of the orders of the echellogram i e the measurements correspond to the wavelengths of maximum efficiency of each order We included only the parts of the spectrum which were well detected and far from the saturation limit lt 13 000 ADU pix The measured fluxes ADU pix are summarized in Tab 8 the values can be transformed in flux of photo electrons using the conversion factor of GIANO array electronics 2 2 el ADU Order um Measured ADU pix in 10s multiply 0 22 to get photons s pix GIANO preslit user manual description and performances 15 Sep 2013 Page 37 of 43 T 108 C T 150 C T 200 C T 250 C T 300 C T 350 C 32 2 398 2090 9820 33 2 325 1480 7350 34
41. re is declared In case it is absolutely necessary to ask to the Arcetri Observatory infrared team the permission of such hazardous thing and to verify their availability for the realignment procedure GIANO preslit user manual description and performances 15 Sep 2013 Page 36 of 43 5 Measurements of efficiency This section summarizes the most significant measurements of absolute and relative efficiencies of GIANO and interfaces 5 1 The absolute efficiency of the GIANO spectrometer The measurements were performed on 2013 July 22 using a commercial certified black body source model CS500 manufactured by DIAS Infrared GmbH emissivity 0 97 The measurement setup is shown in Fig 33 GIANO Black body source ei spectrometer a 1 3 8 e _ a 2 calle 3 Input focal plane of GIANO zi 3 g i 2 VA o 6 i a Z i BB aperture D 60mm 1154 LU 19 5 13 6 L i i Cryostat EEE a i Fig 33 Schematic layout of the setup used to measure the absolute efficiency of the GIANO spectrometer The spectrometer was at operative conditions with all the cryogenic parts stabilized at a temperature of about 80K The only optics at ambient temperature were the lenses and window used to re image the input focal plane of GIANO onto the cold slit As cold slit we used S050 whose width and length 0 093 x 1 12 mm projects onto 2 x 24 pixels of the detector The spect
42. s IMPORTANT NOTE 1 the science fiber is NOT symmetrical so if you unplug the SMA connector you lose the position of the two fibers that has to be vertically disposed with respect to the optical bench The female SMA connector is placed on a standard post mountable XY translation stage Thorlabs model LM1XY that has the possibility to adjust the rotation angle of the fiber after it is mounted and screwed When you will remount the OIG box this is the correct device to rotate to find the correct alignment of the two Science fibers looking at the FLI CCD used in the Fiber Viewer configuration you have to place the image of the two fibers vertically in the same position you have before starting the dismount procedure GIANO preslit user manual description and performances 15 Sep 2013 Page 21 of 43 IMPORTANT NOTE 2 the motor cable of PI M 111 linear stage has a standard DB15 connector It is located under the Traco Power downconverter visible in Fig 19 that MUST be removed in order to have direct access to the DB15 connector Fig 19 Connection cables and fibers of the OIG box 4 Now the OIG Box can be removed It is 20 Kg heavy and first of all you have to uplift of 1 2 centimeters the box in the front zone This to unplug the mechanical joint located in the bottom side that is the ONLY mechanical constrain of the OIG Box The Joint is free to move itself and pay attention not to lose it In any case it is an
43. s BS is the dichroic beamsplitter FM are folding mirrors DM is D shape couple of mirrors remotely controlled File TNG_oig ver6 calibration on fibers_tzz_1 zmx The M111 MICOS PI translation stage controls the position of two D shape mirrors that are custom assembled to permit different observing operating modes as described in the following chapter The final f number of the calibration beam is approximately f 4 with a scale factor of approximately 1 The nominal magnification from the fiber source 400 micron fiber to the final focus is equal to one so the input terminations of the scientific ZBLAN fiber can be fed by the incoming light from the calibration light source that can be chosen between the Ne U lamp and the Halogen lamp The calibration sources are located into the Preslit Rackmount GIANO preslit user manual description and performances 15 Sep 2013 Page 12 of 43 Light path description of the guider camera The Guider is based on a CCD camera made by Finger Lake based on a CCD having 512X512 pixel array of 20 micron pixel size The focal camera is realized using an off axis parabola P3 identical to P2 The scale on CCD is 83 micron arcsec on sky that it means there is a magnification of 0 44 from f 11 TNG focus to the focus on the guider CCD The nominal FOV of the guider is 2X2 arcmin but during sky observation the FOV is partially vignetted by the D shape Mirror support located on the f 11 TNG f
44. s This is compatible with and confirms the large drop in efficiency seen with the airglow lines The above measurements indicate that a large drop of efficiency occurs when GIANO is connected to TNG This variation is found both for point sources stars and for diffuse objects sky background Therefore it cannot be attributed to errors in focusing or centering the objects in the fibers A possible explanation for this annoying problem is that the optical axis chief ray of the telescope at the OIG focus is misaligned relative to the mechanical axis of the Nasmith A interface We have unsuccessfully tried to verify this possibility by visually following the light of a very bright star through the optics of the OIG interface The main limitation was that the dichroic is opaque to optical light and therefore we could not follow the light after the beam splitter To overcome this problem we are purchasing a new dichroic which we plan to install during the commissioning run of October 2013 We made also a few limited attempts to blindly tilt the OIG interface to maximize the background signal from the sky No significant improvement was found GIANO preslit user manual description and performances 15 Sep 2013 Page 43 of 43 Image test_direct Roy 1 Ti 4 8000 GH 3 1 P1 305 A black fiber direct red fiber 0IG_int Ro blue fiber DIG_int TNG z 6000 T o a i 5 4000 f 2 g X 3 E 3 w 2000 R 3 T 3 5 102
45. tinues to be important for the background light reduction we work in a fiber limited condition in which the image of the fiber is itself the slit The Giano Detector pixel size is 18x18 micron Each pixel on the input cold slit has a nominal dimension of 18 micron 11 4 2 47 micron GIANO preslit user manual description and performances 15 Sep 2013 Page 31 of 43 Fig 29 Images of the f 16 focus using calibration light taken at TNG Left without the use of the slicer Right with the slicer In Fig 30 a Zemax simulation of the Bowen Wallraven prism is shown Bowen Walraven image slicers use a thin glass plate where the light is transmitted along by total internal reflection A base prism with a sharp edge is glued to the plate by molecular contact to cut the internal reflection of the transmitted beam By choosing an appropriate configuration the slices are arranged on a line simulating the slit of a spectrograph G Avila 8446 370 SPIE 2012 During the commisiong in July 2013 the used mode was number 4 In this condition we have measured a increasing signal in the Giano detector of approximately 25 using the slicer with respect to not using Fig 30 The Image Slicer of the Giano s preslit based on a Bowen Wallraven prism GIANO preslit user manual description and performances 15 Sep 2013 Page 32 of 43 4 4 Fiber scrambler mechanism The fiber scramble
46. to electrons and D fp The results are summarized in Fig 36 The peak values of efficiency are about 0 091 which once compared with the results shown in Fig 33 indicates a total throughput of the fiber interfaces of about 41 This value is compatible with the measurement performed in Arcetri in June 2013 which yielded a total throughput of about 50 without the image slicer GIANO preslit user manual description and performances 15 Sep 2013 Page 41 of 43 Jul 30 2013 Giano end to end looking at black body Fap se Ne dea pea le ed th oe lly Se ef p 0 08 0 06 End to end efficiency 0 04 T 150 c 0 02 II A I A PE LC em Get AE E SV ERA ES I ARE TA RE IO sm 1 2 1 3 14 15 16 17 18 19 20 2 1 2 2 R 3 2 4 Wavelength um Fig 36 End to end absolute efficiencies of GIANO including the fiber interfaces 5 3 Efficiencies with the telescope and looking directly at the sky The scientific observations of stars with known fluxes were used to compute the instrumental efficiencies The derived throughput was in all cases lower than 1 5 i e much smaller than the end to end efficiency of GIANO Sect 5 2 We repeatedly checked the focusing and centering of the star in the fiber This somewhat cumbersome procedure consisted of taking relatively fast 30 sec spectra at different telescope positions Six spectra with the telescope moved in step of 0 5 in a and other six moving in were
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