the new Hydrogen TPC at PSI

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the new Hydrogen TPC at PSI status report,
Gatchina meeting June 14-17, 2004 by Malte
Hildebrandt and Claude Petitjean

the TPC at first assembly Oct 2002
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• short history of TPC development
• 1997-1999 proposal development of a new
  prototype TPC at Gatchina
• 1998-2000 successful test runs at PSI huge
  problems with gas purity
• and HV stability of the cathode
  planes (currents)
• April 2000 decision to develop high purity
  TPCs ( PCs) at Gatchina PSI
• main features UH vacuum, use
  only UHV proof bakable materials
• (metals, ceramics, glass frames
  with metal coatings, etc)
• develop new soldering technique
  to mount wires under tensions
• May 2003 the PSI-TPC reached -6.5 kV in 10 bar
  protium (good for mips),
• but then developed several
  hotspots (? back to -4.4 kV)
• Aug 2003 stable operation at -4.8 kV (after
  separation of strip voltage
• from upper cathode) good enough
  as perfect µ stop detector

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PSI design drawing of the new TPC
construction with glass frames and ceramic
structure bakable to 130 C
filling 10 bar protium
Ucathodes 5-6 kV
E 2 kV/cm - vdrift 0.5 cm/µs sensitive
volume (12 x 15 x 30) cm3
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TPC anode/cathodes hotspots verified in Oct/Nov
2003 after the runs
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• TPC development since end of 2003 run
• 11.10.2003 sensitivity test for 5.3 MeV
  Alvarez muons
• -5.3kV good for Alvarez µ tracks. TPC
  tripped at this voltage ( EOR)
• mid Oct 2003 TPC moved back to the lab for
  detailed studies,
• a DAQ was setup for automatic voltage
  setting and controls,
• with continuous monitoring of each anode
  wire and strip cathode
• first step verify the TPC behaviour (TPC
  unchanged)
• - 21.10.-19.11.03 5 bar N2, up to -5.8 kV,
  later only -5.2 kV
• - 25.11.-01.12.03 10 bar H2, up to -5.3 kV,
  later only -4.8 kV
• second step clean the whole TPC
• - 03.12.-18.12.03 clean room TPC taken apart,
  all wires inspected, cleaned
• - 18.12.-05.01.04 pumping, outgasing 21 10-6
  mbar/h ? 5 10-8/day _at_10bar
• third step run up the cleaned TPC to reach -5.6
  kV stable operation
• - 06.01.-23.01.04 10 bar N2, -5.65 kV, HV -35.65
  kV (el.Field 2.5 kV/cm)

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electronic setup for TPC lab tests Oct-03 up to
now
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details of TPC test electronics In OLGA lab
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TPC inspection during cleaning in Dec 2003
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voltage developments and currents during
forming in 5 bar N2 (13.-14.5.04)
USC (V) IA (nA)
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final recovery of TPC voltage to -6.0 kV in 5 bar
N2 (14.-16.05.2004)
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electronic scheme of hotspot search during TPC
tuneup
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hotspots seen in 2004 on anode/cathode planes of
TPC
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for comparison hotspots encountered during
Oct/Nov 2003
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electronic scheme of current measurement from
Sr90 beta source
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currents from Sr90 beta source versus electrical
driftfield measured in 5 bar N2 at -5.6 kV
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• outlook
• the PSI TPC is essentially ready to be operated
• at -5.4 kV, good for observing Alvarez muons
• - PC2 is removed, since it failed in 2003 and an
• other geometry was decided for 2004
• - a new entrance flange designed for mounting a
• Gatchina Beryllium window will be ready by the
• end of June-04 (see design drawing)

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new beam entrance flange for Gatchina Be window