Victoria TPC R

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Victoria TPC RDUpdate Outlook

• Gabe Rosenbaum, Dean Karlen, Paul Poffenberger,
  Thanos Michailopoulos, Chris Nell
• University of Victoria

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Outline

• Brief overview of previous activities
• System modifications
• Micromegas setup and tests
• Preliminary results of nitrogen laser tests
• Future plans

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Victoria TPC

• 30 cm drift volume
• 256 channel readout using STAR electronics
• GEM or MicroMegas gas amplification
• Quartz window added for laser tests

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Previous Tests

• Tests done in TRIUMF(1T) and DESY (5T) solenoids
• All test done using double GEM for amplification
• All previous testing done with cosmics

TRIUMF
DESY
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Resolution Drift Direction
P5 gas
drift time resolution (50 ns time bins)
1.6 mm
B-fields from 0 - 5 T
TDR gas
0.8 mm
drift time (50 ns bins)
0 mm
drift time resolution (50 ns time bins)
300 mm
1.6 mm

• A simple time of arrival is used for each row
• Slightly better resolution found with TDR gas

0.8 mm
drift time (50 ns bins)
0 mm
300 mm
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Resolution Transverse Direction (P5 gas)
transverse resolution (mm)
B 0
B 0.9 T
100 micron
B 1.5 T
300 mm
30 mm
drift time (50 ns bins)
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Systematics

• Pad to pad gain variations were studied and
  (shown not to dominate the data)
• Noise was included in Monte Carlo simulation
  (also showed little effect on results)
• We see biases which change with track position
  and increase with B-field (need to account for
  field distortions)

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Data Acquision Changes

• DAQ speed was improved by a factor of 2-3 using
  fiber optic link from VME to PC
• New feature needed to distingish between cosmic
  and laser events

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Data Acquision Changes

• Problem first few time bins were dropped
  affecting the data for very short drifts
• Card was made to bypass the electronics reset
  after data acquisition has begun

Normal reset
No reset
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MicroMeGas - New Test Cell and Pad Array

• New test cell for micromegas end cap
• New pad array made with shorted pads for use with
  micromegas (pad height reduced)

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MicroMeGas - Attaching Resistive Foil

• Sheet adhesive and resistive foil are placed on
  board
• Board is put in steel frame and baked under
  pressure

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MicroMeGas - Tests

• Mesh brought up to 500V on pad array in air with
  little sparking only gt490V
• Resistive foil added
• mesh sparks earlier gt440V and sparking is large
  enough to trip power supply
• So far unable to see an signals on pads with
  micromegas in P10 gas (only had 1 day to try)

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Tests With Nitrogen Laser

• 337 nm UV laser
• 6080 ?J/pulse (maybe)
• Using double GEM setup
• Needs sharp focus to make track
• Laser power varies from pulse to pulse

Laser Setup
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Ionization Depends on Focus
Row 0
Row 1
Row 3
Charge collected on each pad row
Beam focus
Row 4
Row 7
Row 10
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Change of Beam Position

• X0 position changed by 4.5mm between runs
• TPC rotated between runs by 0.08 rad

4.54mm
0.076 rad
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Transverse Resolution
x0 position constant over time
x0 position (mm)
Time (hours)
Residuals in x
x0 distribution
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Plans - Laser Delivery System(for use with DESY
Nd-Yag laser)

• Single track
• Single track resolution
• Gas properties
• Gain
• Distortions in electron transport
• Double track
• Two track resolution
• Ion feed back

• Variable drift distances
• Variable transverse position
• Independent beam locations

Under construction
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Plans Schedule

• Finish laser delivery system (this week)
• Calibrate and align remote control software and
  optical components (next week)
• Travel to DESY for 266nm UV laser tests in
  B-field up to 5T (arrive Aug 10)

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The EndThank you