Virtual Laboratory of Nuclear Fission Virtual practicum in the framework of the project Virtual Laboratory of Nuclear Fission

Transcription

1 Virtual Laboratory of Nuclear Fission Virtual practicum in the framework of the project Virtual Laboratory of Nuclear Fission Khanyisa Sowazi, University of the Western Cape JINR SAR, September 2015

2 INDEX Study of signals from a pulse generator Signal measurements from a semiconductor detector by the use of the oscilloscope Work with the signals from the PIN diode Calibration from the precision pulse generator Work with the CAMAC slave controller. Study of a register module

3 Study of signals from a pulse generator We use generator to create pulses on the oscilloscope. From there we can measure the amplitude and duration of each signal on the oscilloscope. We measure the length of any wire by putting a wire of known length on one channel and the unknown on another channel and then measure the time delay. The signal propagation velocity in the cable is 5 nanoseconds per meter

4 Signal measurements from a semiconductor detector by the use of the oscilloscope

5 We use Cf-252 as our radioactive source and the signal is read by a semiconductor detector. Since the signal generated is on the Nano-ampere scale, we use a high voltage source to amplify the signal. After amplification our oscilloscope can now read the signal and hence we can now do our physics. If the voltage is high enough you should be able to observe two signals, one from alpha decay and the other from fission.

6 Work with the signals from the PIN diode Now here we use CAMAC which has in it a HV generator, modulator, amplifier, QDC and Intelligent Crate Controller. Signals are generated as spectra with all the different amplitudes(volts) and number of signals(counts). We can modulate the gap between each signal by adjusting the amplifier until we get a satisfying spectra. Each channel corresponds to energy, so by analyzing at which channel the peak is, you will get the energy and hence what type of particle is emmitted.

7 Calibration from the precision pulse generator For calibration we use a signal generating amplifier, QDC(Charge-to-Digital- Converter) and intelligent crate controller connected a the computer. We run a few signals from 10 millivolts, moving in steps of ten and see what channels they correspond to. We then make a plot of amplitude(mv) against the number of channels and should have the relationship y = ax + b. Calibration coefficient is and the intercept is

8 Work with the CAMAC slave controller. Study of a register module CAMAC(Computer Automated Measurement And Control) is a control and data acquisition system based on Crates and Modules. It is a crate with 25 slots in which modules are inserted including a control crate. We can choose which slot(station) we read from by adjusting the crate controller which is usually at the top right of the CAMAC crate.

9 Register module.

10 Virtual Laboratory of Nuclear Fission Studying of radioactivity and cosmic rays using scintillation detectors Ndivhuwo Ndou, University of Venda JINR SAR, September 2015

11 Purpose Preparation of the experimental material for the development of new virtual practical works for the project Virtual Laboratory of Nuclear Fission

12 Measurements of signals from a scintillation detector

13 Scintillation detector scheme

14 ADC calibration from the precision amplitude generator

15 Obtaining of the amplitude spectrum from the NaI detector 40 K E = 1416 kev

16 Obtaining of the amplitude spectrum from the NaI detector with radioactive source Source: 85Strontium + 88Yttrium 514 kev 898 kev 40 K 1836 kev Radioactive source

17 Data analysis of spectra in ROOT

18 Data analysis of spectra in ROOT 1416 kev ( 40 K) 514 kev Expected gamma Potassium lines from 898 kev gamma-line from radioactive source 1836 kev NaI impurity

19 Work with the scintillation telescope

20 Conclusion The experimental material for 2 new virtual practicum works for the project Virtual Laboratory of Nuclear Fission was prepared: 1. Work with scintillation detectors 2. Scintillation telescope: study of cosmic rays

21 Virtual Laboratory of Nuclear Fission LISSA training: measurements of thin foil thicknesses by the use of the radium-226 alpha source Ndinannyi Justice Mukwevho, University of the Western Cape JINR SAR, September 2015

22 THE MAIN AIM OF THE EXPERIMENT The main aim of the experiment was to measure the thicknesses of the foils by the use of radium 226 alpha source.

23 DETECTOR HOLDER WITHOUT A FOIL The radium source emits alpha particle which is detected in the PIN diode. The primary function of a preamplifier is to extract the signal from the detector.

24 DETECTOR HOLDER WITH A FOIL The radium source emits alpha particle which passes through the foil and detected in the PIN diode.

25 EXPERIMENTAL SETUP This is the picture showing the experimental setup and the equipment used is vacuum chamber, preamplifier, vacuum station, 226Ra source, Foil (the material of the foil is polycarbonate), CAEN flash-digitizer and PC with data collecting software.

26 Counts 4.784MeV SPECTRA WITHOUT THE FOIL 5.489MeV 7.687MeV 6.002MeV We calibrate by finding a relationship between energy and channels. We start by putting a source of radiation with no foil in-between it and the detector. We get 4 peaks as in the diagram. We find the center of mass for each peak by finding their mean. We found the energies of the four peaks on literature and plot a function of energies against the mean channel values. The slope of the graph is the calibration coefficient we use for converting from channel to energy. We also add the intercept when converting. Channel N

27 CALIBRATION OF SPECTROMETER The calibration graph is represented by a straight line. The data was analyzed by using the relation y = ax + b The coefficient of straight line slope (Calibration coefficient) is

28 Counts SPECTRA WITH THE FOIL We again measure the channel for the four peaks by finding the mean value for each peak. We use our calibration equation (y = ax + b) to get the precise energy for all the peaks. The particle loses some of its energy when passing through the foil. The spectra shifted to the left because of energy loss Channel N

29 CALCULATION OF THICKNESS OF THE FOIL USING SRIM (Stopping and Range of Ions in Matter) SRIM software was used to calculate the thickness of the foil. SRIM is the software that can be used to simulate the interaction of particles with matter

30 Calculation of thickness of the foil using the Stopping and Range of Ions in Matter (SRIM) software

31 Table 1 : shows the thickness of different foils Energy without foil = MeV No. of foil Energy after passing foil (MeV) Thickness(Å)

32 GRAPH OF ENERGY (MeV) vs. THICKNESS(Å) The obtained graph has a linear form The coefficient of straight line slope is E-6 This graph shows that the thicker the foil, the lesser the energy of the alpha particle after passing the foil SO OUR EXPERIMENT WAS STABLE

33 Virtual Laboratory of Nuclear Fission Data analysis of LIS spectrometer signals from 5 GS/s Switched Capacitor Digitizer. Kehinde Gbenga Tomiwa, University of the Witwatersrand JINR SAR, September 2015

34 Experimental setup Determination of particle time of flight of particle Source Apparatus: Pin Diode detector (measures energy and time of flight) Time Stamp detector based on Microchannel plate (measures time of flight) Source Califonium-252 with Plutonium-238 Emits Alphas and fission fragments Start signal Detector signal

35 Analysis of signal Root/C++: Analysis flow Draw shape of the signals Event-by-Event Revert Spectra Fit Pedestal (find baseline) and Smooth Signal Data input: Binary data from Start-TD and PIN diode detector Number of Events: Filter event based on amplitude distribution Determine the Timestamp (TS) for each channel TOF = TSPin Dec -TSStart Dec

36 Detectors signal Spectra TS1 TS2 TOF threshold

37 Event Amplitude Distribution Alpha peak 238 Pu Alpha peak 252 Cf Pin Diode Amp. detector Dist. Fission fragments

38 Detector Spectra y p 0 ts? Fit on Signal pedestal p0 Fit on Signal rise Slope (p1) of fit Xbin number(ns) TS1 TS2 TOF Method Draw amplitude distribution of all event. Define Start signal threshold to filter events Fit signal pedestal and rise time to obtain baseline and slope. Estimate ts for start and pin diode detector event by event

39 Time of Flight Distribution Alpha peak 252 Cf Alpha peak 238 Pu Fission fragments

40 Summary Data from LIS experimental setup was analysed Start detector signal threshold was defined Filter event based on the signal amplitude distribution Time-stamp of signals was estimated Time of flight of particles was esytimated event by event

41 Thank you!