ISC End Station User`s Manual - DCC
Contents
1. esse ese 7 2 2 1 QPD VWbttentnglAntt wbitening 7 2 2 2 Green QPD eum 8 22 3 MS SUSPENSION se EES serene Ke oek isu ee ig Ee Gee kes Es ee De ees ee ee Ep Ke 8 3 ISC End Station Optics Table ses SR Ak EN ed N Ed ee N Ge 9 21 Fiber Beam SelUP ses ER EE SESSE NE ORR EARRE SERE SEE EN R GENE SEE SERS ERA GENE ARE SERE OE GEROER 9 3 1 1 Corner Station Setup es sesde ER ENE NR cient de GE eN Ge EGO Rd 9 3 1 2 Polarization CorrectiOn ee ee ee ee ee ee ee ee ee ee ee ee ee 9 3 2 Prometheus Laser Setup ss Rea RR RR RR AR RR R AA EE ER RR RR RR RARR aa ARE EE EER RR Re 9 3 2 1 EENEG eege 9 3 2 2 Freguency SGD ee ES ee 9 3 2 3 SHG Temperature AGUS iiss ccs ccccctnassinsadsaatnncdenisadncanidaacteandaadmideantanctonededs 10 3 3 Nominal Laser Power Levels ccsccceccesececceeeceeeceeeeeeeeeeuseueeeeeceeeueeeueeneeeees 10 3 3 1 File Path ads Se ee eaea terece aet ee oe ee ee rear ee ee 10 33 2 IR Laser bah 11 3 3 3 Green Laser Pat EE EE RE Ee ER Seengen ege Sege dees 11 3 4 eet di EE OR N EE nnmnnn nnmnnn nnna 11 3 5 Input Steering Mirrors enee 11 3 5 1 SEED EE 11 3 5 2 Controls PDarameters ee ee ee ee ee ee ee ee ee ee ee 12 4 Easer Locking E 12 4 1 Controls ConfigurstiOR ss Ek iN sie EERS KE ERGE De EE EE SES ENR EKKE ER EES SEER EKEN GEE 12 42 Standard Operating Parameters uk 13 4 2 1 elle le EE OE OE N deas 13 4 2 2 Filter and Gain Settings EE GE ES enn neon ene ene ene 13 4 2 3 Performance Check 13 4 3 Faure Mo2. polarity of the locking 3 2 2 2 Temperature Adjust The coarse adjustment of the laser frequency needs to be done with the crystal temperature A higher temperature corresponds to a lower frequency However mode hopes will occur every 2 C and reset the frequency back by some amount Use an RF spectrum analyzer with at least 500 MHz bandwidth to look for the beat note on the broadband LSC detector FIBR_A The initial frequency can be off by GHz which might be too far off to be detected by the photodetector Scan the temperature until the beat note appears Then adjust it approximately to the desired frequency There is an interaction between the laser diode current adjust and the crystal temperature We use this to make sure we are in the middle of a mode hopping region First move the temperature up and down and watch for the mode hope If the desired frequency is close to a mode hope region adjust the diode current by 0 1 A and try again Repeat this procedure until the desired frequency is near the approximately centered between two mode hope regions 3 2 3 SHG Temperature Adjust Monitor the green laser power and make sure that the temperature of the SHG is adjusted to deliver maximum green power 3 3 Nominal Laser Power Levels 3 3 1 Fiber Path The nominal power levels in the fiber path are as follows Parameter Nominal Minimum Reference cavity transmission 10 mW Coupled into fiber 7mW
3. v4 3 ISC End Station Optics Table 3 1 Fiber Beam Setup 3 1 1 Corner Station Setup On the PSL table a portion of the reference cavity transmission is coupled into the fiber for ALS We start with 9 mW in the path towards the fiber and get 70 coupling into the fiber This fiber goes to the Fiber Distribution Box document tree E1200121 It has a 160 MHz AOM when this AOM is driven the outputs for each end station contain just under 10 of the input power There are PDs controlled by the slow controls system that monitor the power into the fiber the power received in the fiber distribution box They have medm screens which are accessible under DCPDs under LSC on the sitemap These should be calibrated by setting the responsivity and the nominal powers set The end station PLL autolocker will generate an error message if the power is low on these PDs 3 1 2 Polarization Correction The outputs from the fiber distribution box goes to a polarization controller located in the MSR MPC1 the manual is available at T1200496 From here it is launched into the fiber to the end station arriving at the end station with about 50 75 loss We need at a minimum 40 uW coming out of the fiber at the end station again there are DC PDs monitoring this power and the polarization of the output These PDs need to be calibrated and limits and nominal values set The PLL autolocker also checks the values of these PDs and will generate error messages when the
4. 4mW Receive in MSR 300 uW 100 uW Send to end station 300 uW 100 uW Receive at end station 150 uW 50 uW On ISC table 150 uW 40 uW On monitor photodiode FIBR TRANS 9 uW 2 5 uW On fiber locking photodiode FIBR_A 75 uW 40 uW 10 LIGO LIGO E1300903 v4 3 3 2 IR Laser Path The nominal power levels for the IR path of the Prometheus laser are as follows Parameter Nominal Minimum Laser output 1 1 W 100 mW After attenuation 50 mW 25 mW On monitor photodiode LASER_IR 350 uW 100 uW On fiber locking photodiode FIBR A 25 mW 600 uW 3 3 3 Green Laser Path The nominal power levels for the green path of the Prometheus laser are as follows Parameter Nominal Minimum Laser output 20 mW 10 mW After first Faraday isolator 17 mW 8 mW On monitor photodiode LASER GR 800 uW 400 uW After second Faraday isolator 14 mW 6 mW At periscope into vacuum chamber 12 mW 5 mW Return from ETM on reflection photodiode REEL A 12 mW 3 mW Return from ETM on reflection photodiode REFL_A 12 mW Received at ISCT1 X arm lt 5 mW Received at ISCT1 Y arm lt 5 mW 3 4 Beam Alignment 3 5 Input Steering Mirrors 3 5 1 Setup The manual for the PZTs and controllers are available at E1300870 The controllers should be operated in the low bandwidth mode To do this you need to move a jumper in the controller instructions are in the manual The input steering PZTs have two axes Y rotates yaw an
5. B FE for green injection monitor B in the ALS End station overview will open the QPD overview for a corresponding QPD Press whiten button and read the numbers in the whitening gain slider There are three stages of switchable analog whitening and digital anti whitening for all four quadrants of each of QPDs The state of these can be monitored by the same screen as the whitening gain slider It is extremely important that whitening and anti whitening stages are LIGO LIGO E1300903 v4 enabled disabled as a pair If not e g whitening stage 2 is on but anti whitening stage 2 is off check the nominal status by trending HI ALS Y QPD A WHITEN FILTER 2 and H1 ALS Y OPD A AWHITEN SET2 etc and determine if they are enabled or disabled There is a non switchable analog whitening stage and a corresponding anti whitening stage in FM4 of the input filter for each quadrant You should not disable these but if you suspect that they are disabled open each of the filters e g from the aforementioned QPD overview by pressing buttons labeled as SEG1 SEG2 etc 2 2 2 Green QPD sum Check if the light level on the green QPDs is nominal see Table 1 If the sum is significantly lower first check if anything is coming in to the digital system Check the whitening settings see the previous section move the whitening gain slider up and down and see if you re getting any signal Don t forget to restore the slider back to norm
6. LIGO LASER INTERFEROMETER GRAVITATIONAL WAVE OBSERVATORY LIGO Laboratory LIGO Scientific Collaboration LIGO E1300903 v4 Advanced LIGO 12 17 2013 ISC End Station User s Manual Daniel Sigg Keita Kawabe Sheila Dwyer Kiwamu Izumi Stefan Ballmer and Alexa Staley Distribution of this document LIGO Scientific Collaboration This is an internal working note of the LIGO Laboratory California Institute of Technology Massachusetts Institute of Technology LIGO Project MS 18 34 LIGO Project NW22 295 1200 E California Blvd 185 Albany St Pasadena CA 91125 Cambridge MA 02139 Phone 626 395 2129 Phone 617 253 4824 Fax 626 304 9834 Fax 617 253 7014 E mail info ligo caltech edu E mail info ligo mit edu LIGO Hanford Observatory LIGO Livingston Observatory P O Box 159 P O Box 940 Richland WA 99352 Livingston LA 70754 Phone 509 372 8106 Phone 225 686 3100 Fax 509 372 8137 Fax 225 686 7189 http www ligo caltech edu LIGO LIGO E1300903 v4 Table of Contents 1 Inirodue TOI EE 4 1 1 Bloc do Di Ui ARE oo 4 1 2 IN NAMEN ME eto 4 1 3 DET e EE 4 14 Applicable Documents ske ENE RR ee ee REK NE Wee ee Ee GEENEEN ee esse 5 2 ge ET TEE 5 21 Controls COmPQUIA OI reens R EER EERDER ER REAGEER ce cteeee EeAE RR RADE ER Re R iN Rea bee RR EE 5 2 1 1 TMS Beam Centering Zap Ese Oes EE Ee EE EER EED 6 2 1 2 TMS SUSPENSION ER EE 6 2 1 3 IR Transmission Monitor 7 2 2 Standard Operating Parametere ees
7. al after this If you re not getting anything you need to call a CDS or ISC expert If the readbacks are alive the problem might be that the output of the QPD centering servo railed because of some unusual circumstance e g somebody blocked the beam for a short period To verify this first turn off the beam centering servo for all four filters then reset the integrators of the servo by pressing Clear All History button If you are getting some light in both of the QPDs turn on the servo again If not check if the offsets in the PZT output filters are lost Open the PZT output filter screen by pressing buttons labeled PZT1 PIT etc check the offset in the filter it should be enabled and non zero If the offsets are off enable them If the offsets are zero burt restore them as necessary If the offsets for all four filters are non zero and enabled trend these offsets and see if the current numbers are significantly different from a known good time Set them back to the known good values If that doesn t recover the sum check if the TMS suspension bias is on and if there is a large offset Trend H1 SUS TMSY M1 OPTICALIGN P OUTPUT etc and compare the current numbers with the known working numbers If the green QPD sums are still too low call an ISC expert 2 23 TMS Suspension Usually the TMS suspension should be damped with an alignment bias These are handled in the same way as quad suspensions LIGO LIGO E1300903
8. ance Checks 5 3 Failure Modes
9. d X rotates 11 LIGO LIGO E1300903 v4 Pitch They operate with inputs from 0 10V so the initial alignment should be done with 5V input to the controllers Before the initial alignment the sensor offset should also be adjusted according to the manual Once the initial alignment is done and the TMS offsets set so that the retroreflection returns to the PD the alignment of optics near the PZTs should be adjusted so that the beam is centered on the TMS QPDs when they are operated at the middle of their range 3 5 2 Controls Parameters 4 Laser Locking 4 1 Controls Configuration The autolocker for locking the PLL is in the Twin CAT library a state diagram is available at T1300891 The autolocker screen is available by clicking on the small grey box labeled X ARM PLL or Y arm in the ALS overview screens at each end station The autolocker checks several locking conditions if any of these are not met an error message will appear at the bottom of the screen and the locking conditions text will have a red background To clear all of these each of the relevant DC PDs will need to be calibrated and some of them will need to have limits set 12 LIGO LIGO E1300903 v4 4 2 Standard Operating Parameters 4 2 1 Conditions 4 2 2 Filter and Gain Settings 4 2 3 Performance Checks 4 3 Failure Modes 5 Cavity Locking 5 1 Controls Configuration 5 2 Standard Operating Parameters 5 2 1 Conditions 5 2 2 Filter and Gain Settings 5 2 3 Perform
10. deS ii ies deene EES cs Sasa sack Hevea ah cae coh ans GR aes eas ee 13 LIGO LIGO E1300903 v4 5 Cavity TOC MING AE AE RE N N EE N EN 13 5 1 Controls ConfidUuralOM is EE SE SEEK KEER GEE GE EKEN EE GEE GE WENE wee GE De EE 13 5 2 Standard Operating Parameters ee ii R RR RR RR RR RR RR RR RR RR RR Re RE 13 5 2 1 bl le ie Sa oP EE AA EE N Ee HEN 13 5 2 2 Filter and Gain ie CN 13 5 2 3 Performance CHEERS EE De ED De OE ED De De 13 5 3 Faure Mode ie Es DE a Ge Sey ee De ek aa toner 13 LIGO LIGO E1300903 v4 1 Introduction This manual covers the setup and operations of the interferometer sensing and control equipment located in the end station 1 1 Block Diagram 1 2 Naming 1 3 Operations screens Under the ALS button on the site map Figure 1 MEDM Site Map ALS button and end station SUS buttons are highlighted here There should be two buttons named End X Overview and End Y Overview which are linked to the ALS overview screen of corresponding end stations Figure 2 H1 aLIGO SITE MAP gen am er eas Hae on ees zm ene EES EER oer 1 is om To own f EE mesc Een vert ost Toto on st py EET err ws gees wo sn ES HeadURL https redoubt ligo wa caltech edu svn cds_user_apps trunk cds h1 medm SITEMAP adl 1067716842 Z Id SITEMAP adl 6172 2013 11 04 21349 552 sheila dwyer LIGO ORG Figure 1 MEDM Site Map ALS button and end station SUS buttons are highlighted
11. here LIGO LIGO E1300903 v4 ini d ALSEndRef ILockeds1ou0F kedSlo ETE HT EE EI FIT ALIGNMENT SERVO Ee BERE He YAU ALIGNMENT SERVO Hm Dm ALIGNMENT THRESHOLIS Figure 2 ALS X overview screen 1 4 Applicable Documents 2 Transmission Monitor The Transmission Monitor comprises a beam reduction expansion telescope an IR QPD sled to monitor the transmission of 1064 nm beam from the arm cavity a green QPD sled to monitor 532 nm beam injected from the end station ISCT to the BSC The entire structure is suspended by the Transmission Monitor Suspension TMS The transmission monitor system as a whole is sometimes also referred to as TMS 2 1 Controls Configuration The ALS End station overview MEDM screen Figure 2 provides convenient links to most of important TMS functionality Two PZT mirrors on the in air ISC table ISCTEX and ISCTEY will change the green beam pointing into the chamber and the green QPD sled is used as the sensor to monitor the alignment of the green beam into the TMS telescope Together they are used for a beam centering servo to automatically align the green beam to the TMS LIGO LIGO E1300903 v4 Once the green beam is fixed to the TMS via the servo the TMS suspension biases change the pointing of
12. nominal zero 2 1 2 TMS Suspension The TMS suspension is used to change the angle of the TMS telescope which in turn changes the green beam pointing towards the ETM and thus ITM From the ALS End station overview you can directly adjust the bias sliders to the TMS suspension If there is a problem with the TMS suspension you should open the TMS suspension MEDM screen Figure 3 to further diagnose the problem LIGO LIGO E1300903 v4 Figure 3 TMS Suspension screen In this example the master ON OFF switch is off the first of the four red vertical bars next to the right most green bar and the watchdog DACKILL are also tripped three red bars next to the master switch so nothing should be working 2 1 3 IR Transmission Monitor IR QPD sled output and associated ASC and LSC servo boxes are in a red rectangle above the green QPD centering servo box Figure 2 2 2 Standard Operating Parameters Parameter Value Whitening gain for IR QPDs Number of whitening anti whitening stages for IR QPDs Whitening gain for green QPDs Number of whitening anti whitening stages for green QPDs Minimum light level on the green QPDs normalized sum field gt 0 7 Nominal unity gain frequency of the green beam steering servos Table 1 Standard Operating Parameters for the Transmission Monitor 2 2 1 QPD Whitening Anti whitening Pressing buttons like TR A FE for transmission monitor A or QPD
13. polarization drifts or the power drops The polarization needs to be adjusted manually using MPC1 when it drifts far enough 3 2 Prometheus Laser Setup The Prometheus manual can be found in LIGO T1000643 The Prometheus has a noise eater for intensity stabilization which should be disabled The noise eater can oscillate making it impossible to lock the PLL until someone resets it There is a noise eater monitor available on the laser head which is available in the laser MEDM screen but this does not work and sometimes indicates that there is no oscillation when there is in reality an oscillation 3 2 1 Power Adjust Adjust the laser diode current near its nominal settings as indicated by the data sheet belonging to the specific laser Sometimes the factory setting indicates that the current should be set to the maximum in this case set it slightly below the maximum 3 2 2 Frequency Setup 3 2 2 1 Nominal Frequency Nominal frequencies are listed in LIGO T1300883 The X end stations are using a down shifted laser frequency whereas the Y end stations are using an up shifted laser frequency The X end LIGO LIGO E1300903 v4 stations are using a down shifted laser frequency whereas the Y end stations are using an up shifted laser frequency The PLL autolocker screen is available from the small grey box that says X or Y Arm PLL in the corner of the ALS overview screen On this screen you can choose Above PSL or below PSL to set the
14. the green beam leaving the telescope without affecting the beam path on the telescope When the IR light resonates inside the arm cavity an IR QPD sled will work as an ASC sensor for the interferometer A fraction of the IR beam is also directed towards the ISC table where a high gain photodiode is used to measure light levels during lock acquisition Once the interferometer control transitions to science mode a beam diverter will guide the IR beam leaving the vacuum towards an in vacuum beam dump 2 1 1 TMS Beam Centering Servo On the bottom right of the ALS End station overview Figure 2 the graphics inside a green rectangle are for the green QPD sled represented by two X Y monitors and the beam centering servo some buttons and matrices in black rectangle The input of the servo is the QPD error signal and the output is connected to the PZT mirrors To turn the servo on or off click the ON OFF button of four servo filters This toggles the on off indicator of each filter between green ON and red OFF In Figure 2 all filters are off The servo filters have an integrator so disabling the servo means that the output of the filters are held constant until the servo is turned on again This is convenient as turning them on off doesn t suddenly throw the alignment off When desired you can reset the servo filters by Clear all history button The PZT control voltage is unipolar OV to 10V and is biased to mid range 5V for a
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