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FYS-KJM5920

Nuclear Measurement Methods and Instrumentation

Purpose of the lab-course is to learn about these modules/systems and methods:

• Electronic modules, data acquisition system and sorting of events • Properties of LaBr3 scintillators • Response functions, efficiencies and coincidences

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1 Gamma-response functions (week 1) Use a 37 kBq 60Co and a 37 kBq 22Na source for the measurements. The sources were purchased 1. Oct. 2016 . What is the activity of the two sources to day?

1. Choose one of the OSCAR detectors to measure singles gamma-spectra. Make a drawing of the set-up with names of the modules and cables used.

2. Write a half page of the properties of the OSCAR detectors (search on web for LaBr3(Ce) crystals). What is the physical size of the OSCAR detectors?

3. Measure the background and spectra with a 60Co source in 15, 20 and 25 cm distance from the detector surface.

4. What is the main contribution to the background. 5. Subtract background from the spectra measured with the source. 6. What is the solid angle in the three runs and check if the count rate follows

a 1/r2 law? 7. Measure the size of the lead collimator. 8. Repeat point 4 and 5 with a collimator in front of the detector.

2 Coincidence measurements (week 2)

1. Make a drawing of the coincidence set-up. 2. Put the 60Co source in the middle of OSCAR (without collimator) and

record the events on disk. 3. Study the sorting routine and understand the main purpose of the routine. 4. Gate on the 1.33 MeV peak and find the efficiency of OSCAR for 1.17

MeV gammas. 5. The two gammas are correlated in the angle between them, by the intensity

W(q) = 1 + cos2(q)/8 + cos4(q)/24. Can you confirm this? 6. Calculate the efficiency of the detector(s) assuming an internal efficiency of

100% and the solid angle used. Compare with the result of point 4. 7. Energy calibrate the spectrum. 8. Record events from a 22Na source and determine the gamma lines. 9. Gate on 511 keV and 1275 keV line and study the coincidences for the 90

and 180 dgrs detectors.

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3 Some useful mama commands AR ARithmetic's (+-/*) CA Get info and give a0, a1 and a2 and dimension CE Change between Channel and Energy display CO COmpress spectrum CR Call CursoR and get info DS DiSplay spectrum DX M1 M2 Low/high markers for Display of X axis DY M1 M2 Low/high markers for Display of Y axis DZ M1 M2 Low/high markers for Display of Z axis EX EXpand display using cursor (mouse) FD Fit Data points with polynomial, exponential, etc. FO FOld spectrum with the response matrix FT N N=1-15: set-up for N peaks and do fit GR Get Response matrix into working matrix 1 or 2 HE List commands IC Select spectrum LS LiSt files in current directory (ls from UNIX) DM Display Matrix as spectra OS OVerlay of spectra PO POlynom fit to set of data PF Peak Find on spectrum or matrix PM Project Matrix down on X or Y axis RE REad spectrum RM Make Response Matrix SC N SCale for Y axis: N=1/2/3=lin/quadratic/log10 SD Sirius Display, display acquisition spectra ST STop and exit Mama SU M1 M2 SUm counts between channel M1 and M2 using cursor UN UNfold spectrum with response matrix WR WRite spectrum with calibration and dimensions