Method for digital particle spectrometry Khryachkov Vitaly Institute for physics and power engineering (IPPE) Obninsk, Russia
The goals of Analog Signal Processing Signal amplification Signal filtering Analyzing of signals amplitude distribution Analyzing of signals timing distribution
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
Use of Digital Signal Processing in different fields Communication Radar and sonar Music Mobile phone Geology Photography Medicine
Advantages of Digital Signal Processing Stability Resettability Depth of evaluation Low mass of the equipment
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
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. -1-15 15 b) 1 5-5 -1-15 5 1 15 2 25 3 15 1 5-5 -1-15 5 1 15 2 25 3 c) 5 1 15 2 25 3 Time, channel
Preamplifier Preamplifier Stop Digitizer Filter Input Spectroscopy amplifier Analog and digital spectrometric channel Detector ADC Computer Detector Computer Logical unit Delay Unit
Amplitude, channel How do the digital signals from the particle detector look like? 9 8 7 6 5 - CsI - Anode 1 - Anode 2 - Cathode 4 3 2 1 1 2 3 4 5 6 Time, mks
Amplitude, channel Signal Amplitude Spectroscopy Amplifier Amplitude, channel Signal Amplitude Analog spectroscopy amplifier 8 1 6 8 6 4 4 2 2 1 2 3 4 5 6 7 Time, mks 1 2 3 4 5 6 7 Time, mks
Amplitude, channel Value Amplitude, channel Digital spectroscopy amplifier 8 Convolution 1 6 1, 8 4 2 * =,5, -,5-1, 6 4 2 1 2 3 4 5 6 7 Time, mks 5 1 15 2 25 3 Time, mks 1 2 3 4 5 6 7 Time, mks
Amplitude, channel Transient process Another method for amplitude determination 9 8 Zero line Saturated signal 7 6 5 M K 4 3 2 1 N 1 2 3 4 5 Time, channel A K s( i) N im i 1 K M 1 s( i) N
Amplitude, channel Amplitude Digital Converter (ADC) 1 9 85 8 8 2,9 3, 3,1 3,2 3,3 6 Maximum 4 2 1 2 3 4 5 6 7 Time, mks
Amplitude, channel Discriminator with fix threshold 6 5 4 T 3 2 Threshold 1 12 14 16 18 2 22 24 Time, channel
Amplitude, channel Delay unit 1 8 6 4 2 Initial signal 1 2 3 4 5 6 7 8 8 6 4 2 t Delayed signal 2 3 4 5 6 7 8 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!
Amplitude, channel Constant Fraction (CF) discriminator 16 14 a) 12 1 8 6 4 2-2 33 34 35 36 37 38 39 4 1 5-5 -1-15 b) -2 33 34 35 36 37 38 39 4 16 14 c) 12 1 8 6 4 T S 2-2 33 34 35 36 37 38 39 4 Time, ns Delayed initial signal + Inversed and attenuated initial signal = Sum of signals
I A, channel Determination of the signal appearance time with a constant fraction discriminator for digital signals. 15 12 9 - original shifted signal - reflected and scaled signal - summ of signals 6 3 Zero time estimation 42 44 46 48 5 52 54 56 58 time, ns
Amplitude -Amplitude Амплитуда New possibility for signal evaluation 3 -Amplitude 25-5 2 15 1 T S T L Amplitude inversion -1-15 -2 T S T L 5-25 -3 1 2 3 4 5 6 Time, channel 1 2 3 4 5 6 Time, channel Time inversion -5-1 -15 T L T S -2-25 -3 1 2 3 4 5 6 -Time, channel
Current, channel charge, channel Charge determination 1 8 14 12 6 4 1 8 6 2 4 2-2 2 3 4 5 6 Time, channel -2 2 3 4 5 6 Time, channel
CsI(Tl) scintillator Pu-Be neutron source collimator CsI(Tl) scintillator polyethylene radiator 226Ra source PM FEU-118
226 Ra decay scheme
CsI(Tl). Spectrometer PMT Anode Fast amplifier PMT Dinode Fast amplifier CF Delay unit Input Stop WFD CAMAC Bus Computer
I, a.u. CsI(Tl). Pulse shape for different particles 4 35 3 - - -p 25 2 15 1 5 2,5 3,75 5, 6,25 Time, mks
Ln(, a.u.) I, a.u. Decomposition of CsI(Tl) signal 25 2 8 Super-slow 15 7 1 6 Slow 5 1 5 4 8 3 Fast 6 2 4 2 1 2 4 6 8 1 12 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
Ln(, a.u.) How to understand 3D spectra? 8 7 Super-slow 11 488, 6 Slow 235,8 113,9 5 4 55,5 26,6 3 2 Fast 12,85 6,29 3, 1 2 4 6 8 1 12 P A, channel
Luminescence decay time for the CsI(Tl) scintillator 7 N 6 1 =357(+-4) ns 5 4 3 2 =1287(+-25) ns 2 1 2 4 6 8 1 12 14 16 18, ns
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 12 1 1 p 8 8 6 c.-s. #1 c.-s. #2 6 p 4 4 2 2 24 22 2 18 16 14 12 1 8 6 4 2 2 4 6 8 1 12 P A, channel Fast component area Sf -2 7 72 74 76 78 8 82 84 86 88 9 Time, channel Total signal area N N 28 24 2 16 12 8 4 2 4 S Total, a.u. 6 8 1 c.-s. #1 p 5 1 15 2 25 3 1 1 1 1 c.-s. #2 p,1 1 2 3 4 5 6 P Fast, a.u.
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, 2 4 6 8 1 12 S A, channel
1 N 8 6 4 2 7 6 5 4 3 2 1 8 6 4 2 1 8 6 4 2 x1 x1 x1 The CsI(Tl) scintillator for particle identification 4 6 8 1 12 S A, channel All p
Block scheme of a spectrometer based on a stilbene crystal
Amplitude, channel Stilbene. Pulse shape for proton and electron with light yield of 1 MeVee 1 - neutron - gamma ray 1 1 34 36 38 4 42 44 46 48 5 52 54 56 58 Time, channel
counts Stilbene. Amplitude distributions. Digitizer vs conventional electronics 8 7 6 5 4 3 2 1 - WFD - ADC 1 2 3 4 5 6 7 A, channel
Current, channel Pulse area (2 ns), a.u. Stilbene. Pulse shape (PS): Fast versus total area 24 22 Fast component area Sf 1 252 Cf(sf) V=1.8 kv 2 18 Total signal area 8 241 Am 16 14 12 1 6 n 8 6 4 4 2-2 7 72 74 76 78 8 82 84 86 88 9 2 Time, channel 75 15 225 3 375 45 Energy, eekev
Correlation Correlation I A, channel I A, channel Stilbene. Pulse shape discrimination Separation and Correlation 6 4 4 3 2 2 n 1 n 9 6 6 - - n 5 4 3 - - n 3 2 1 2 4 6 8 1 Time, ns 2 4 6 8 1 Time, ns
Correlation Correlation I A, channel I A, channel Stilbene. Pulse shape discrimination Separation and Correlation 2 25 18 16 2 14 12 1 8 6 n 15 1 5 4 2 3 35 2 4 6 8 1 25 2 - - n 3 25 2 - - n 15 15 1 1 5 5 2 4 6 8 1 Time, ns 2 4 6 8 1 Time, ns
Correlation ampl., a.u. Stilbene. PS: Correlation versus total area 1 8 252 Cf(sf) V=1.8 kv 241 Am 6 4 2 n 75 15 225 3 375 45 Energy, eekev
M(A) Stilbene. Double Integral Method vs Correlation method 1 9 8 two integrals correlation 7 6 5 4 3 2 1 2 4 6 8 1 12 14 16 18 2 A, eekev
Stilbene. TOF: comparison of digitizer and conventional electronics 1 N -TDC -WFD 1 1 1 1 1 15 2 25 3 35 4 Time, ns
Stilbene. TOF with PSD N 1 1 - All - Gamma - Neutron 1 1 1 1 15 2 25 3 35 4 Time, ns
Proportional counter (PC). Block diagram of the experimental setup with a proportional counter FA fast amplifier, PA preamplifier, CFD constant fraction discriminator
PC. Signals from the anode of a proportional counter Q, rel. units I A, rel. units S, rel. units Q A, rel. units 6 4 2 1 5 n 1 4 T Ç 1 3 1 2 1 1 25 2 15 1 5 1 4 T,Ç 1 3 1 2 1 1 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 n T 1 2 3 4 5 Time, channels + + + + - - - - + + + - - - + + - - Proton Electron
T+2, channels T+2, channels PC. Energy vs drift time Thermal neutron + γ 6 Co (γ ray) 12 PuBe source in polyethylene 1 12 -rays 6 Co 1 8 8 6 6 4 4 2 2 2 4 6 8 1 12 Amplitude, channels 2 4 6 8 1 12 Amplitude, channels
I Max, channels PC. Amplitude of the anode signal vs maximum of the current pulse 7 6 5 4 3 2 1 2 4 6 8 1 12 Amplitude, channels
PC. The energy resolution improving N 1 1 1 1 5 1 15 2 25 3 35 Amplitude, channels The energy resolution improved from 5.2% to 4%, A response function became much better.
Ionisation chamber D x R θ + - ) cos( 1 D X e n Q Q Cth An R dx x x n X ) ( 1
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
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
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.
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
232 Th(n,f), En=1,2 and 5 MeV 232 Th(n,f) 7 Y, % En=5. MeV 6 En=1.2 MeV 5 4 3 2 1 4 6 8 1 12 14 16 18 1,1,1 4 6 8 1 12 14 16 18 Mass, a.m.u.
(Q * -TKE), MeV 238 U(n,f), En=5 MeV 1 8 6 4 2 6 8 1 12 14 16 Fission fragment mass, a.m.u.
I A, channel Q A, channel 238 U(n,f), En=5 MeV. Cold fission. 16 14-1 MeV 12 12 1 1 8 8 6 6 4 4 2 2 6 8 1 12 14 16 18 4 2 1-2 MeV 3 16 14 12 2 1 8 6 1 4 2 6 8 1 12 14 16 18 28 5 2-3 MeV 24 22 4 2 18 3 16 14 14 18 26 4-5 MeV 6 8 1 12 14 16 18 5-6 MeV 6 8 1 12 14 16 18 6-7 MeV 9 8 7 6 5 4 3 2 1 3 25 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. 1.25 2.5 3.75 5. 6.25 35 2 12 1 8 2 1 6 4 2 15 8 7 6 6 8 1 12 14 16 18 3-4 MeV 35 3 6 8 1 12 14 16 18 7-8 MeV 1 5 5 4 25 2 3 2 1 15 1 5 6 8 1 12 14 16 18 6 8 1 12 14 16 18-5 2.9 3. 3.1 3.3 3.4 3.5 3.6 3.8 3.9 4. 4.1 Time, mks Mass, a.m.u..
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 4,15 9 8 7 6 5 4 3 2 1 1. Insulator 2. Cathode 3. Grid 4. Anode 5. Shielding electrodes 6. Target - CsI - Anode 1 - Anode 2 - Cathode 1 2 3 4 5 6 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
Fast exp. area, a.u. Measurement of probability of spontaneous ternary fission of 252 Cf 12 252 Cf(sf) 1 8 6 T 4 p D 2 2 4 6 8 1 12 Energy, a.u.
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.