MS4 Manual
Contents
1. Dale B W Longworth C O and Johnson C E 1985 Mossbauer Spectroscopy and its Applications Cambridge Univ Press Debrunner P G 1993 Mossbauer Spectroscopy of Iron Proteins in Biological Magnetic Resonance 13 eds Berliner L J and Reuben J Plenum New York 59 101 Edwards P R Johnson C E and Williams R J P 1967 Mossbauer Spectra of Some Tetrahedral Iron I Compounds J Chem Phys 47 2074 2082 Fee J A Findling K L Tatsuro Y Hille R Tarr G E Hearshen D O Dunham W R Day E P Kent T A and M nck E 1984 Purification and Characterization of the Rieske Iron Sulfur Protein from Thermus thermophilus J Biol Chem 259 124 133 Fraunfelder H 1963 The M ssbauer Effect W A Benjamin New York Greenwood N N and Gibb T C 1971 Mossbauer Spectroscopy Chapman and Hall London Huynh B H and Kent T A 1984 in Advances in Inorganic Biochemistry eds Eichhorn G L and Luigi G M Elsevier New York 163 223 Ingalls R 1964 Electric Field Gradient Tensor in Ferrous Compounds Phys Rev 133 3A A787 A795 Lang G 1970 Mossbauer Spectroscopy of Haem Proteins Quart Rev Biophysics 3 I 1 60 Lang G and Marshall W 1966 Mossbauer Effect in Some Hemoglobin Compounds Proc Phys Soc 87 3 34 Mossbauer R 1958 Kernresonzflureszenz von Gammastrahlung in 191 7 Physik 151 124 143 Preston R S Hanna S S and Heberle J 19622. Mossbauer Effect in Metallic Iron Phys Rev 128 2207 2218 Press W H Flannery B P Teukolsky S A and Vetterling W T 1986 Numerical Recipes Cambridge University Press Cambridge Rancourt D G and Ping J Y 1991 Voigt based methods for arbitrary shape static hyperfine parameter distributions in Mossbauer spectroscopy Nucl Instr Meth B58 85 97 Thosar B V and Iyengar P K Eds 1982 Advances in Mossbauer Spectroscopy Elsevier New York Varret F 1976 Crystal Field Effects on High Spin Ferrous Ion J de Phsyique Collogue CG Supplement 12 Tome 37 437 456 Whittaker J W Lipscomb J D Kent T A and M nck E 1984 Brevibacterium fuscum Protocatechuate 3 4 Dioxygenase Purification Crystallization and Characterization J Biol Chem 259 4466 4475
3. SEE Co W202 Gamma ray Spectrometer Kr Gas Proportional Counter made by LND Inc MS Windows PC with USB interface ot aS lS The MS4 software installed on the PC includes the W202 control program the W302 control program and the WMOSS Mossbauer spectral analysis software Also the MS4 includes a group license for the WMOSS software allowing WMOSS to be installed on other PC s within the customer s local work group Defining dual SCA Mossbauer Spectrum windows in Puls display in Multi Channel Kr Gas Counter Hight Spectrum Scaler Mode Sample W202 Control W302 Control O gt Ray Source Motion Drive amp Feedback TE f Resonance O Ray Spectrometer Figure 2 Schematic Diagram of the MS4 Spectroscopy System Select an area sufficiently stable and without vibrations Vibrations will superimpose on the linear motion of the motor and will change the Doppler shift of the photons which will distort the Mossbauer spectrum SEE Co MS4 Mossbauer Spectroscopy System Manual Page 4 Figure 3 MS4 Room Temperature Version The MS4 Support Frame comes pre assembled Source shield and counter shield are included W302 RGS unit shown behind the VT400 velocity transducer ae Support Frame Ze Figure 4 _MS4 Low Temperature Version The MS4 Cryogenic Support Frame comes pre assembled and provides for positioning the velocity transducer and gamma detector around the tail of a cryostat Source shield and counter sh
4. clicking on Set Window 1 A vertical line appears on the PHA plot and a set of 4 Arrow buttons and one OK button appear to the right of the Get Data check box Use the Arrow Buttons to move the cursor on the plot to the left edge of the peak to be counted Then click OK This defines the voltage level for the Lower Level Detector for SCA 1 Click the Arrow Buttons again to define the width of the window When the right edge of the window is at the right edge of the peak click OK Set the window for SCA 2 by clicking the Set Window 2 command button and following the same procedure as for SCA 1 See Fig 12 L window windowy2 i windows counter B Formt Jog Figure 12 Setting the window for SCA 2 a 3 gt pan set set window Ml window2 x counter lt After setting both windows click Send Windows to transfer the window settings to the dual SCA s in the W202 This action clears the windows from the screen and sends the window information from the PC to the W202 hardware The Counts Out signal will now be a stream of TTL pulses generated by detector events that have a peak voltage height that falls within Window 1 or Window 2 These counts are routed to the W302 Resonant Gamma ray Spectrometer Counts 1 In or Counts 2 In when collecting a Mossbauer spectrum Close the W202 PC program The W202 will continue to generate the dual SCA output pulses until its power is removed or its settings c
5. is many orders of magnitude greater than the background radiation and we shall henceforth refer to the gamma beam as if it were 100 Mossbauer radiation unless we specifically note otherwise We shall also assume that the nuclear levels of the source are not split and the energy distribution of the beam is given by a single Lorentzian SEE CO e 7385 Bush Lake Rd e Edina MN 55439 e USA Tel 952 831 0409 e FAX 612 395 5558 e e mail info seeco us SEE Co MS4 Mossbauer Spectroscopy System Manual Page 2 57 2I 837 keV I 7 2 t 270 days Electron Capture 57 136 keV I 5 2 14 4 keV I 3 2 T 14x 10 sec 0 I 1 2 Figure 1 Decay scheme of Feoi frommii parent Co97 The red oval specifies the transition that generates the 14 4 keV Gammas that are counted for the M ssbauer experiment 8 4 of Co57 decays cause a 14 4 keV Gamma to be emitted Of those a fraction f are recoil free Modulation of the Gamma ray energy via the Doppler Shift To use our M ssbauer source as a spectroscopic tool we must be able to vary its energy over a significant range This is accomplished by Doppler shifting the energy of the gamma beam Moving the source at a velocity of 1 mm sec toward the sample will increase the energy of the photons by 14 4 keV v c 4 8 x 10 8 eV or ten natural line widths The mm sec is a convenient M ssbauer unit and is equal to 4 8 x 10 8 eV for Fe A M ssbauer spectrometer consists of a source wh
6. reduces the gamma counting efficiency Often non resonant absorption by the sample in a transmission mode experiment will reduce the 6 keV rate so that the X rays are not a problem If not then a high pass filter can be placed in the beam to absorb the 6 keV X rays before they enter the detector Figure 10 shows the effect as placing a 1 mm thick paper filter in front of the detector window amp Formi le x Figure 10 a Same experiment as Fig 5 but with 1mm paper filters in beam The 6 keV Fe X ray peak is suppressed relative to the 14 keV Gamma peak and the 2 keV Escape peak Also the Escape peak at 10 keV due to the 22 keV Rh X rays is now partially resolved set Gas counter windowst window2 W SEE Co MS4 Mossbauer Spectroscopy System Manual Page 8 Once the beam geometry is defined we set the Single Channel Analyzers SCA windows Two independent SCA s windows exist in the W202 hardware The two SCA s are provided to optimize the system for counting the 14 keV Gammas detected by a Kr gas counter Approximately 1 3 to 1 2 of the 14 keV gammas absorbed in a Kr gas counter generate a 12 keV Kr X ray that leaves escapes the counter without interacting with the gas For those escape events only a net energy of 2 keV is deposited in the detector by the 14 keV Gamma Hence the peak at 2 keV is observed in the PHA spectrum B Formt Figure 11 Setting the window for SCA 1 Set the window of SCA 1 by
7. the W202 is connected to a Kr gas counter detector use the arrow buttons in the lower right corner to set the voltage to approximately 1750 Volts Again after the HV has been changed it can take as long as 20 s for the voltage at the detector to stabilize Once the HV is stable and if you have a Co 57 gamma source shining on the detector window you will see the pulse height spectrum growing in amplitude as shown in Fig 9 The actual HV required depends of the particular detector and the gain and filter settings in the W202 Normally for a Kr gas counter with 1 atmosphere Kr CO2 gas pressure and a 0 002 inch diameter center wire the HV will be in the range of 1 500 V to 2 000 V SEE Co MS4 Mossbauer Spectroscopy System Manual Page 7 I Formi L Figure 9 The pulse height spectrum f of a 25 mCi Co 57 Mossbauer source with a Rh matrix The source to detector distance was 8 cm A Pb shield with a 1 2 cm diameter B aperture was in front of the Kr gas counter Acquisition time was approximately 10 s zet set Gas window E window2 i counter From left to right the peaks are the 2 keV Escape peak due to the 14 4 keV y rays the 6 keV Fe X rays the 14 4 keV y rays and the 22 keV Rh X rays For Fe 57 M ssbauer spectroscopy the 14 keV Gamma peak and the 2 keV Escape peak need to be counted The 6 keV X rays are unwanted At higher count rates they can generate pulses in the detector that overlap in time with the pulses due to the gammas which
8. Science Engineering amp Education Co Helping you SEE the data SEE Co Model MS4 Mossbauer Spectroscopy System User Manual The SEE Co Model MS4 is a highly integrated efficient and convenient system for the acquisition and analysis of Mossbauer Spectra This manual contains a brief introduction to Mossbauer Spectroscopy and describes the design and use of the MS4 hardware and software INTRODUCTION Mossbauer Spectroscopy is Resonant Gamma ray Spectroscopy RGS All nuclei possess excited states some of which are accessible from the ground state by photon absorption Often the excited states of the absorber are long lived and the range of photon energies which will resonantly excite the absorption is extremely narrow If strong absorption is to be observed a significant fraction of the energy of the source radiation must be within this range Such a source may obviously consist of excited nuclei of the same isotope as the absorber The excited nuclei may be decay products of appropriate parent nuclei It was once thought that conservation of momentum requires the recoil of the emitting nucleus and that the photon would not have the full transition energy and hence would not resonantly excite the absorber If the nucleus is free the recoil momentum and energy are taken by the nucleus itself In a solid the momentum and energy go into lattice vibrations i e phonons The temperature dependence of the absorption cross section of Ir 1 l
9. by double clicking on the W202 icon on your desktop A dialog box as shown in Figure 7 will appear The drop down list will show all W202 units connected to the PC Select the unit you require and then click OK SEE Co MS4 Mossbauer Spectroscopy System Manual Page 6 Select Device Figure 7 Initial Select Device dialog box Clicking the down arrow will display a list of all W202 units connected to the PC w202 sn010 After the Select Device form closes the Main Form of the W202 PC software will appear as shown in Fig 8 The central area is used to plot the pulse height spectrum On the right is a vertical bar graph that indicates the DC voltage applied to the detector in Volts The voltage is controlled by clicking on the arrows below the vertical bar graph After changing the voltage it takes 10 to 20 seconds to stabilize the voltage at the detector before which an accurate pulse height spectrum will not be generated Use the Clear button to remove any data collected during the time of unstable voltage Di Formi Figure 8 W202 Main Form set set window window Clicking TEST causes internally generated pulses of two fixed heights to be routed to the peak detector input This verifies the proper working of the W202 independent of the detector The positions of the test pulses on the PHA plot are independent of the high voltage setting Click on Gas Counter to activate the input from the detector If
10. ed M ssbauer 1958 to be the first to realize that a photon could be emitted with the entire solid recoiling as one rigid mass The energy lost to the recoil in this situation is negligible and the emitted photon may resonantly excite the absorber Resonant Gamma ray Spectroscopy is commonly called Mossbauer Spectroscopy in honor of its discoverer Prof Rudolph M ssbauer See http nobelprize org nobel_prizes physics laureates 1961 mossbauer bio html Nuclear Physics of Fe The isotope with the strongest recoilless resonant absorption is Fe gt Since the vast majority of the work reported in the Mossbauer literature is for iron this discussion is limited to that isotope Figure 1 shows the decay of Fe from its parent Co Of all the excited Fe nuclei about 10 will emit a 14 4 keV gamma ray via a magnetic dipole transition from the metastable I 3 2 state to the I 1 2 ground state I is the nuclear spin The ratio of recoil free 14 4 keV photons to all the 14 4 keV photons emitted is f the recoil free fraction of the source f varies with the properties of the solid and decreases monotonically with increasing temperature The line width of the emitted radiation is limited in theory by t the mean life of the I 3 2 state In Fe t 0 14 micro sec and the energy distribution is given by a Lorentzian with a full width at half maximum of Ihat 4 7 x 10 eV Lang 1970 The intensity per unit energy of the Mossbauer radiation
11. hanged via the W202 PC program The W202 PC program is only used to set the dual SCA windows and does not need to be running to collect a M ssbauer spectrum SEE Co MS4 Mossbauer Spectroscopy System Manual Page 9 W302 Setup and Operation Figures 13 and 14 show the front and rear views of the W302 Resonant Gamma ray Spectrometer Figure 15 depicits the internal organization of the W302 and its external connections Figure 13 Front view of the SEE Co Model W302 Resonant Gamma ray Spectrometer Case dimensions are 190 mm x 250 mm x 90 mm SEE CO RESONANT GAMMA RAT APECTROMETER HOTEL Fiz Figure 14 Rear view of the SEE Co Model W302 Resonant Gamma ray Spectrometer The primary internal components are 1 C8051f120 8 bit MCU with 12 bit ADC and 12 bit DAC 64 kByte dual port RAM C8051 320 with USB interface Variable gain Velocity Sensor amplifier Variable gain and variable bandwidth Drive amplifier 08052120 N I 2 a C8051f320 8 bit MCU ual po 8 bit MCU u i W302 Resonant Gamma Ray Spectrometer n VT400 S Tp Drive Signal 12 bit DAC lt P TD ja Velocity Sensor Signal 12 bit ADC C Source 25 MHz Clock Sample MCS Address MCS Data SCA M ssbauer Spectrum Output W202 SEE Co MS4 Mossbauer Spectroscopy System Manual Page 10 References Belozerski G N 1993 Mossbauer Studies of Surface Layers Studies in Physical and Theoretical Chemistry 81 Elsevier Amsterdam Cranshaw T E
12. ich may be moved relative to the sample and a counter to monitor the intensity of the beam after it has passed through the sample The M ssbauer spectrum is a plot of the counting rate against the source velocity i e the beam energy If the sample nuclear levels are not split and the I 3 2 to I 1 2 transition energy equals that of the source then the effective cross section for absorption is a function of gamma energy as given by Fraunfelder 1963 Sf 21 1 ie f Fii eq 1 21 1 2m Alta E Ey That where I 1 2 and uS 2 are the ground and excited nuclear spins 9 0 is the internal conversion coefficient ratio of betas to gammas in the 14 4 keV decay A 8 61 x 10 cm is the wavelength of the radiation E Ey is the difference between mean incident and resonant gamma energy lhat is the energy width of the excited nucleus and f is the probability of recoilless absorption The spectrum will be a single Lorentzian centered at v 0 with a linewidth FWHM of 2l hat 0 19 mm sec The line width is 21 pat since the observed line arises from the convolution of the source energy distribution and absorber cross section SEE Co MS4 Mossbauer Spectroscopy System Manual Page 3 MECHANICAL SETUP Figure 2 shows the relationship of the primary components of the MS4 hardware Those components are Gamma source manufactured by Ritverc GmbH SEE Co VT400 Linear Velocity Transducer SEE Co W302 Resonant Gamma ray Spectrometer
13. ield are included W202 unit shown connected to Kr gas counter SEE Co MS4 Mossbauer Spectroscopy System Manual Page 5 W202 Setup and Operation SEECo s Model W202 Gamma ray Spectrometer provides both pulse height analysis and dual single channel analysis The user interface is connected via a USB link to a Windows PC The W202 SCA TTL pulse output may be routed to the input of a separate Multi Channel Scalar e g a SEE Co W302 In the following it is assumed that the W202 is part of a Mossbauer spectrometer with a Kr gas proportional counter Other applications of the W202 are possible Figure 5 Zara nn ee Front and Rear views of the SEE Co WEB RESEARCH CO W202 Gamma ray Spectrometer anaita ig Dimensions are 5 cm x 10 cm x 12 cm a SEE Co was formerly named WEB count Research Co New W202 units display the SEE Co name LVPS Input i To 120VAC 5 pin DIN Female 12 Er Gas wonten ADC Input To PC USB Port ADC Trigger SCA Control Shaping Sensitive Amp C 605120 Fre am p 86 bit MCU To W302 Counts In Port BNC SCA OUT SMA Figure 6 W202 Block Diagram and External Connections Connect cables as shown in Figure 6 and then plug in 120 VAC outlet or battery backed UPS The W202 has no on off switch If a computer was purchased with the W202 user interface software will be already installed If not see the W202 PC software documentation for installation instructions Start the program
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