1. Pakistan Institute of Engineering and Applied Sciences (PIEAS)
Applicability of Parallel Plate Avalanche Detector Systems to Spontaneous Fission from Cf252
Zafar Yasin
Pakistan Institute of Engineering and Applied Sciences (PIEAS)
Islamabad

2. Outline Importance of Nuclear Fission
Parallel Plate Avalanche Detectors
Spontaneous Fission
Data Analysis
Introduction to MAX-lab electron Accelerator

3. Introduction
Nuclear fission covers the areas ranging from nuclear structure models to accelerator- driven systems.
Spontaneous fission source 252Cf is used for calibration of detectors.
Photon induced fission is as important as fission induced by nucleons.
Photofission has applications in nuclear waste management.
Parallel Plate Avalanche Detectors (PPADs) are fabricated at MAX-lab and tested using 252Cf.
PPADs will be used to study Spontaneous at the MAX-lab electron accelerator.

4. Principle of Parallel-Plate Plate Avalanche Detectors
PPADs lie among the new categories of gas detectors.
Gas multiplication occurs in a PPAD and number of secondary electrons obey the relation given by,
N (d) = N0 exp (α. d),
where
N0 = number of primary electrons,
d = drift path,
α = first Towsend coefficient,
Voltage pulse generated by a fission fragment is given by
where C is the capacitance of the detector.

5. Properties of Parallel-Plate Plate Avalanche Detectors
Capability to handle high count rates up to fissions/s.
Good time resolution up to 500 ps.
Insensitivity to radiation damage.
Clean pulse height separation between fission fragments and lighter charged particles.
High detection efficiency and large solid angles.
Insensitive to neutrons, photons and electrons.
Quite transparent to a high energy photon beam.
Low production cost.

6. A rectangular target-detector arrangement used in the experiment.
Construction of PPADs
A rectangular target-detector arrangement used in the experiment.

7. Construction of PPADs A circular PPAD. Electrode foils
Electrodes frame
Electrode foils
A circular PPAD.

8. Experimental setup for spontaneous fission source 252Cf

9. The reaction chamber in the experimental hall

10. The PPADs mounted inside the reaction chamber

11. CFD
ADC2
PPAD2
PPAD1
Attenuator
Pre-amplifier
Cf252
OR/AND
ADC1
LATCH OR
TDC
Scaler2
Scaler1
Gate generator
Fan out
VETO
Four fold logic unit
Computer
Stop
Start
Stop2
Stop1
NIM
ADC
Gate
Fanout
Interrupt
Delay
Schematic overview of the electronic setup used to study the spontaneous fission from 252Cf.

12. Count rate as a function of voltage and pressure using a PPAD for a 252Cf .

13. Effect of pressure on count rate at constant voltage.

14. Data analysis
Offline analysis is performed using the computer code ROOT.
The ROOT software is an object-oriented (C++) data analysis package developed at CERN.
It was developed keeping in mind the high energy physics experiments and several laboratories around the world use ROOT for the analysis of data.
For the analysis of Spontaneous and photofission data, we have written C++ codes within the ROOT framework.

15. Data analysis

16. Time Spectrum from both PPADs.
Data analysis
Time Spectrum from both PPADs.

17. Energy Spectrum from a PPAD.
Data analysis
Energy Spectrum from a PPAD.

18. Data analysis
A three-dimensional and two dimensional view of the distribution of fission fragments observed with ADC1, x-axis with cut TDC1, versus ADC2, y-axis with cut TDC2.

19. Δt2exp = Δt2kin + Δt2geom + 2 Δt2intr
Time resolution
If the intrinsic time resolutions of the start and stop detectors are equal, then we can write,
Δt2exp = Δt2kin + Δt2geom + 2 Δt2intr
In the present geometry the value of the Δtkin comes out to be 0.6 ns and Δtexp 1.25 ns. If we assume the Δtgeom to be .17 ns, then the intrinsic time resolution is 0.76 ns.
A three-dimensional view of the distribution of fission fragments observed with TDC1 versus TDC2.

20. MAX-lab Electron gun Linac e- MAX I ring Nuclear physics area
Synchrotron
radiation e-
Nuclear
physics
area
MAX-lab

21. Photon tagging Eγ = E0 - Er Detector TDC Target Reaction Product
Photons
Magnet
Radiator e-
Focal Plane Detectors
Faraday cup
Stop
Start
Eγ = E0 - Er

22. Thank you