Method for digital particle spectrometry Khryachkov Vitaly

Size: px

Start display at page:

Download "Method for digital particle spectrometry Khryachkov Vitaly"

Cassandra Day
6 years ago
Views:

1 Method for digital particle spectrometry Khryachkov Vitaly Institute for physics and power engineering (IPPE) Obninsk, Russia

2 The goals of Analog Signal Processing Signal amplification Signal filtering Analyzing of signals amplitude distribution Analyzing of signals timing distribution

3 Analog unit and its function Spectroscopy amplifier Fast amplifier Constant fraction discriminator Discriminator with fix threshold Amplitude to digital converter Time to digital converter Delay unit

4 Use of Digital Signal Processing in different fields Communication Radar and sonar Music Mobile phone Geology Photography Medicine

5 Advantages of Digital Signal Processing Stability Resettability Depth of evaluation Low mass of the equipment

6 Why Digital Spectrometry wasn t used in nuclear physics before? Signals in nuclear physics are fast, non periodical, contain specific noise. Big volume of information

7 Amplitude Nyquist frequency 15 1 a) To properly digitize signal with 5 frequency F, it must be sampled -5 at 2F samples/sec or higher b) c) Time, channel

8 Preamplifier Preamplifier Stop Digitizer Filter Input Spectroscopy amplifier Analog and digital spectrometric channel Detector ADC Computer Detector Computer Logical unit Delay Unit

9 Amplitude, channel How do the digital signals from the particle detector look like? CsI - Anode 1 - Anode 2 - Cathode Time, mks

10 Amplitude, channel Signal Amplitude Spectroscopy Amplifier Amplitude, channel Signal Amplitude Analog spectroscopy amplifier Time, mks Time, mks

11 Amplitude, channel Value Amplitude, channel Digital spectroscopy amplifier 8 Convolution 1 6 1, * =,5, -,5-1, Time, mks Time, mks Time, mks

12 Amplitude, channel Transient process Another method for amplitude determination 9 8 Zero line Saturated signal M K N Time, channel A K s( i) N im i 1 K M 1 s( i) N

13 Amplitude, channel Amplitude Digital Converter (ADC) ,9 3, 3,1 3,2 3,3 6 Maximum Time, mks

14 Amplitude, channel Discriminator with fix threshold T 3 2 Threshold Time, channel

15 Amplitude, channel Delay unit Initial signal t Delayed signal Time, channel You can transfer signal to any time without any distortion of it shape. You can transfer signal not only to the right but to the left too!

16 Amplitude, channel Constant Fraction (CF) discriminator a) b) c) T S Time, ns Delayed initial signal + Inversed and attenuated initial signal = Sum of signals

17 I A, channel Determination of the signal appearance time with a constant fraction discriminator for digital signals original shifted signal - reflected and scaled signal - summ of signals 6 3 Zero time estimation time, ns

18 Amplitude -Amplitude Амплитуда New possibility for signal evaluation 3 -Amplitude T S T L Amplitude inversion T S T L Time, channel Time, channel Time inversion T L T S Time, channel

19 Current, channel charge, channel Charge determination Time, channel Time, channel

20 CsI(Tl) scintillator Pu-Be neutron source collimator CsI(Tl) scintillator polyethylene radiator 226Ra source PM FEU-118

21 226 Ra decay scheme

22 CsI(Tl). Spectrometer PMT Anode Fast amplifier PMT Dinode Fast amplifier CF Delay unit Input Stop WFD CAMAC Bus Computer

23 I, a.u. CsI(Tl). Pulse shape for different particles p ,5 3,75 5, 6,25 Time, mks

24 Ln(, a.u.) I, a.u. Decomposition of CsI(Tl) signal Super-slow Slow Fast P A, channel, 1,25 2,5 3,75 Time, mks S / *exp( ( t T ) / ) S / *exp( ( t T ) / ) L( t) Fast Fast Fast Slow Slow Slow

25 Ln(, a.u.) How to understand 3D spectra? 8 7 Super-slow , 6 Slow 235,8 113, ,5 26,6 3 2 Fast 12,85 6,29 3, P A, channel

26 Luminescence decay time for the CsI(Tl) scintillator 7 N 6 1 =357(+-4) ns =1287(+-25) ns , ns

27 Current, channel P (t=4 ns), a.u. S Fast, a.u. CsI(Tl). Two methods of particle identification Integration in the window Fast component area p c.-s. #1 c.-s. #2 6 p P A, channel Fast component area Sf Time, channel Total signal area N N S Total, a.u c.-s. #1 p c.-s. #2 p, P Fast, a.u.

28 CsI(Tl). Comparison of two methods R,6,5 -S F method -S (t=4 ns) method p R S S,4,3,2,1, S A, channel

29 1 N x1 x1 x1 The CsI(Tl) scintillator for particle identification S A, channel All p

30 Block scheme of a spectrometer based on a stilbene crystal

31 Amplitude, channel Stilbene. Pulse shape for proton and electron with light yield of 1 MeVee 1 - neutron - gamma ray Time, channel

32 counts Stilbene. Amplitude distributions. Digitizer vs conventional electronics WFD - ADC A, channel

33 Current, channel Pulse area (2 ns), a.u. Stilbene. Pulse shape (PS): Fast versus total area Fast component area Sf Cf(sf) V=1.8 kv 2 18 Total signal area Am n Time, channel Energy, eekev

34 Correlation Correlation I A, channel I A, channel Stilbene. Pulse shape discrimination Separation and Correlation n 1 n n n Time, ns Time, ns

35 Correlation Correlation I A, channel I A, channel Stilbene. Pulse shape discrimination Separation and Correlation n n n Time, ns Time, ns

36 Correlation ampl., a.u. Stilbene. PS: Correlation versus total area Cf(sf) V=1.8 kv 241 Am n Energy, eekev

37 M(A) Stilbene. Double Integral Method vs Correlation method two integrals correlation A, eekev

38 Stilbene. TOF: comparison of digitizer and conventional electronics 1 N -TDC -WFD Time, ns

39 Stilbene. TOF with PSD N All - Gamma - Neutron Time, ns

40 Proportional counter (PC). Block diagram of the experimental setup with a proportional counter FA fast amplifier, PA preamplifier, CFD constant fraction discriminator

41 PC. Signals from the anode of a proportional counter Q, rel. units I A, rel. units S, rel. units Q A, rel. units n 1 4 T Ç T,Ç n T Time, channels Proton Electron

42 T+2, channels T+2, channels PC. Energy vs drift time Thermal neutron + γ 6 Co (γ ray) 12 PuBe source in polyethylene rays 6 Co Amplitude, channels Amplitude, channels

43 I Max, channels PC. Amplitude of the anode signal vs maximum of the current pulse Amplitude, channels

44 PC. The energy resolution improving N Amplitude, channels The energy resolution improved from 5.2% to 4%, A response function became much better.

45 Ionisation chamber D x R θ + - ) cos( 1 D X e n Q Q Cth An R dx x x n X ) ( 1

46 Ionisation chamber with Frisch grid e n Q An ) cos( 1 D X e n Q Cat R dx x x n X ) ( 1 E, cos(θ) D x R + - θ d

47 Pulse shape for IC with Frisch grid n e T EK Q К =n e(1-(x/d)cosθ) P c2 P c3 Q Cat n e 1 X D cos( ) P c1 Charge T SC Time P a Q n e An -n e T SA1 T SA2 Т EA Q а =-n e

48 CFD Delay unit Input A Stop Input B Input C Wave form digitizer Computer Net CAMAC Fission fragments spectrometer. o CSPA FA Anode FA Grid Cathode CSPA H V o o Grid 238U FA Anode CSPA FA High voltage filter High voltage suplay o Ionization chamber: d=12 mm, height 9 mm. Working gas: Ar+1%CH4, Pressure.75 atm. Digitizer: LeCroy 2262, 4 МHz, Time scale 7 μs. 238 U sample sizes: Diameter - 6 mm. Thickness 25 μg/cm 2. Energy resolution 4 kev for 6 MeV α-particles. Angular resolution -.65 (in cos(θ) unit). Mass resolution ~1 a.m.u.

49 Fission fragment spectrometer properties Energy of both fragments Mass of both fragments (2E method) Emission angles of both fragments Bragg curve for both fragments Control of pile up On line measurement of electron drift velocity (working gas property on line control) Energy losses in the target correction Direct Frisch grid inefficiency measurement

50 232 Th(n,f), En=1,2 and 5 MeV 232 Th(n,f) 7 Y, % En=5. MeV 6 En=1.2 MeV ,1, Mass, a.m.u.

51 (Q * -TKE), MeV 238 U(n,f), En=5 MeV Fission fragment mass, a.m.u.

52 I A, channel Q A, channel 238 U(n,f), En=5 MeV. Cold fission MeV MeV MeV MeV MeV MeV Anode 1 Anode 2 M1=14.25 M2=98.75 E1=8.4 E2=114.2 cos(1)=.522 cos(2)=.515 TKE=194.6 MeV MeV MeV Time, mks Mass, a.m.u..

53 amplitude, channel, 1-1 % TKE. MeV, barn Ionization chamber Measurement of probability of ternary fission of 232 Th and 238 U by Obninsk - 96 fast neutrons 7 o 4 1 Anode FA 1 5 Dinode FA 2 CFD CU DU HV o 6 o 2 PMT А1 PA1 Catode FA 3 FA 4 CFD Stop WFD S1 S2 S3 PA2 FA 5 S4 3 А2 PA3 FA 6 o 4, Insulator 2. Cathode 3. Grid 4. Anode 5. Shielding electrodes 6. Target - CsI - Anode 1 - Anode 2 - Cathode Time, mks,1,5, 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2, 2,1 2,2 2,3 2,4 2,5 163,5 163, 162,5 162, 161,5 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2, 2,1 2,2 2,3 2,4 2,5 3, 2,5 2, 1,5 1,,5, 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2, 2,1 2,2 2,3 2,4 2,5 Neutron energy, MeV

54 Fast exp. area, a.u. Measurement of probability of spontaneous ternary fission of 252 Cf Cf(sf) T 4 p D Energy, a.u.

55 Conclusions Now digital signal processing for particle registration can work. This method allows us to perform the same operation as the analog unit does. We can make more complicated evaluation of digital signals and extract additional information. We can reach better stability and resettability of obtaining results. Promising results for different types of detectors were obtained.

K 223 Angular Correlation

K 223 Angular Correlation K 223.1 Aim of the Experiment The aim of the experiment is to measure the angular correlation of a γ γ cascade. K 223.2 Required Knowledge Definition of the angular correlation