1. 1

2. 2

3. 3

4. 4

5. 5

6. 6

7. 7

8. 8

9. 9

10. 10

11. 11

12. 12

13. 13

14. 14

15. 15  A) Pulse Height Spectroscopy  Identify the equipment such as detector, electronics modules and NIM bin.  Note down detector type, size, operating voltage and its polarity.  Read the manuals of NIM modules particularly input requirements and output specifications and its principle of operations.  Connect the circuit diagram as shown in Figure.  Apply high voltage to the preamplifier.  Connect the amplifier out put to an oscilloscope.  Ensure that the detector power supply has the same polarity as the detector voltage polarity, otherwise change the polarity on the power supply.  Switch on the detector power supply and apply the detector voltage.  Watch amplifier signal on the oscilloscope. You may not see the signal on the oscilloscope.  Now place a gamma ray source near the detector. Observe the amplifier unipolar or bipolar pulse, as selected by you, on the oscilloscope.

16. 16 A) Optimization of the Shaping Time of the Pulses:  Connect the output of the amplifier to input of the linear gate stretcher(LG)  Select normal mode of the LG and connect to the input of the MCA.  Acquire the pulse height spectrum of the detector pulse height in MCA.  Calculate the FWHM and peak centroid of gamma ray peak in the spectrum  Calculate percentage energy resolution of the detector by dividing FWHM by peak centroid and multiplying it with 100.  Record the shaping time and corresponding % energy resolution of the detector.  Then change the shaping time and record the % resolution for three or four more readings.  Then plot energy resolution as a function of shaping time in an excel sheet.  From the graph determine the optimum shaping time of the amplifier.

17. 17 Integral Spectrum Measurement :  Connect the output of the amplifier to input of the SCA.  Select Normal mode of the SCA and connect its output to a counter.  Adjust the counter period as 2-3 seconds depending upon the count rate of your detector.  Raise the SCA lower level (LL) and upper level (UL) to the maximum.  Note down the LL of the SCA and counter average reading( out of five readings).  Record LL of SCA and corresponding counter average reading in a table.  Lower LL of the SCA in steps of 0.2 and corresponding average counts up till a value of 0.1 for LL of SCA. Record all these values in an excel sheet to plot a graph of counter readings vs LL of SCA.  Plot LL of SCA vs counter reading.  For gamma ray source with single peak, the spectrum shows only one step distribution.  Repeat the above mentioned procedure with a source with two well resolved gamma source such as Bi209.  Plot LL of SCA vs counter reading  Then plot energy resolution as a function of shaping time in an excel sheet.  For gamma ray source with two peak, the spectrum shows two step distribution.