1. Pad Response Function Nuclear Physics Group Institute of Physics, Academia Sinica
Jia-Ye Chen

2. Nuclear Physics Group Meeting, IPAS
Outline
Time Projection Chamber
Pad Response Function (PRF)
Smearing Effect to PRF
Parameterization of PRF
Experimental Measurement
Analysis
Future Work
Nuclear Physics Group Meeting, IPAS

3. Time Projection Chamber
The Time Projection Chamber, T. Lohse and W. Witzeling, C.E.R.N.
Nuclear Physics Group Meeting, IPAS

4. Electric Field Lines with the Gate
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5. Nuclear Physics Group Meeting, IPAS
TPC Gating Modes
Drift Velocity
Drift Volume Length ~ Clock ~
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6. Nuclear Physics Group Meeting, IPAS
Gate Wire
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7. Nuclear Physics Group Meeting, IPAS
FADC Pulses
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8. Nuclear Physics Group Meeting, IPAS
Pad Response Function
Width of PRF
Direct measure of the power to distinguish between two close-by coordinates.
Determine the two-track resolution.
The induced charge distribution is called “Pad Response Function”.
Nuclear Physics Group Meeting, IPAS

9. Parameterization of PRF
Under the optimal design of pad width
G : the distance between sense wire and cathode plane
: chamber-specific pad response width, often normalized to the pad width ΔP by
Nuclear Physics Group Meeting, IPAS

10. Smearing Effects to PRF
The transverse diffusion
The angular wire effect
The angle under which the tracks cross the wire-normal.
The E × B effect close to the sense wires
The angular pad effect
If tracks cross the normal on a pad-row under a non-zero angle.
If more than one wire contributes to a pad signal.
Nuclear Physics Group Meeting, IPAS

11. Smearing Effects to PRF
transverse diffusion coefficient
drift velocity of electron
drift length
wire spacing
Lorentz angle due to ExB effect
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12. Experimental Measurement
New TPC
Line Fitting (Lab. Frame)
By Nakatsugawa Yohei
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13. With & W/O Normalized ADC
X(mm)
ADC
2D Histogram
2D Profile
Normalized
W/O Normalized
Why normalized?
Uniform sum of ADCs.
Smooth the spikes.
Eliminate the saturation of ADC.
Pulse1 : peakADC1
Pulse2 : peakADC2
Pulse3 : peakADC3
Normalize to sum of three peakADCs.
→ peakADC?/sumPeakADC
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14. Nuclear Physics Group Meeting, IPAS
2D Histogram Slices =
Normalized
W/O Normalized
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15. Drift Length Dependence
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16. Nuclear Physics Group Meeting, IPAS
FWHM of the PRF
TRIUMF TPC
Pad rows are parallel to the sense wire.
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17. Angular Wire Dependence
Pad Response Width
Angle (track,wire)
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18. Nuclear Physics Group Meeting, IPAS
Angle(pad,wire)
From layer 1 to 13, total 986 pads.
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19. Coupled Geometry Dependence
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20. Nuclear Physics Group Meeting, IPAS
Simulation to PRF
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21. Nuclear Physics Group Meeting, IPAS
What I ever tried
Layer Dependence → Pad size dependence
Charge Dependence → No dependence
With E×B Effect → Ntuples can NOT be used to study PRF
Drift Length Dependence → Small Dependence
Nuclear Physics Group Meeting, IPAS

22. Nuclear Physics Group Meeting, IPAS
Future Work
Check drift length dependence again.
Normalize PRF simulation.
By 2D fitting to PRF, to get the transverse diffusion coefficient DT.
Nuclear Physics Group Meeting, IPAS