1. “MUON” Collaboration meeting
Tracking system
PNPI Status report
A.Krivshich
June 14, 2004
“MUON” Collaboration meeting
Gatchina, Russia

2. for μp-capture experiment
Tracking system
for μp-capture experiment E
РС 1
РС 2
ТРС
μ - muons

3. Proportional chambers and PC-2
Two sets of PC2 electrodes under production.
It order to finish the PC2 production and start its testing we would propose to discuss and fix a possible amount of materials in the PC2 cathodes during this workshop.
New design of cathode.
Aluminum. Thickness 40m. Soft.
Aluminum. Thickness 40 m. Hard.
Aluminum. Thickness 10m. Soft.
Aluminized Mylar (50m).
Old design of cathode.
Diameter of wires 55m. Stainless steel.
Wire spacing is 1 mm.

4. Time Projection Chamber
TPC#1. It is tested about 15 months.
TPC#2. It is tested about 3 months.
TPC#3. It has to be assembled after finishing
of TPC#1 and TPC#2 tests.

5. TPC production chain Frame manufacturing at PNPI Print circuit
depositing at
STU
Electrode
wiring
at PNPI
Ultra sound
cleaning
Dust control by
light emission in
nitrogen
TPC assembling
in clean room
TPC testing
in vessel
Nitrogen
Hydrogen
Gas supply system

6. ТРС № 1 Date of TPC birth – 18 February 2003
90Sr
Old (PNPI) vessel
Date of TPC birth – 18 February 2003
Туре of vessel - Old one (PNPI)
Gas admixtures
Oxygen Nitrogen Water
After filling ≤0.5 ppm ≤0.5 ppm ≤1 ppm
One month after filling ≤1 ppm ppm ≤ 1 ppm

7. Testing results- Idc ≤ 2nA (HV = 6500V)
TPC#1. Stage # 1
Gas Nitrogen
Pressure Bar
Training period days
Training results - Idc ≤ 2nA (HV = 7000V)
Testing period months
Heating conditions C; 24 hours; 4 times.
Tests duration months.
Testing results- Idc ≤ 2nA (HV = 6500V)

8. Test results - Idc ≤ 5nA (HV = 6500V)
Pressure Bar
Testing period days
TPC#1. Stage # 2
Date of start – 4 February 2004
Gas - Hydrogen
Test results - Idc ≤ 5nA (HV = 6500V)
Outer cathode wire has been broken
in the solder point.
Chamber was disassembled.
The wire was taken out.
Chamber was assembled again.

9. Results of the TPC#1 electrodes Dark current after chamber assembling
visual inspection
No traces of dust.
No dark spots on the anode.
A few light-gray spots (2-3mm diameter) have been observed on the cathode planes.
Dark current after chamber assembling
Idc ≤ 5nA (HV = 6500V)

11. Periodic breakdowns occurred
Breakdown current
exceeded 50A under HV=6500V.
Time interval between
the breakdowns under irradiation
by 90Sr source
67 hours …………………. HV=5300V
48 hours …………………. HV=5400V
48 hours …………………. HV=5500V
6 hours …………………. HV=5600V
Long term operation characteristics of TPC#1 under irradiation
At HV = 5200V (I = 2nA)
No breakdowns during one month

12. Conclusion about TPC#1.
1. The results obtained during more than one year of TPC#1 operation looks quite well. We believe that TPC design and technology of its assembling are reliable and quite promising.
2. A couple of days ago TPC#1 has been taken out from the vessel to study the reasons of breakdowns.
3. The main possible reason of the breakdown occurring is the charge accumulation on the dielectric with consequent discharge.
4. Very probable that main reason of breakdowns is some mistake during TPC assembling.

13. ТРС #2
90Sr
Date of TPC birth – 24 March 2004
Туре of vessel - New one (PNPI+PSI)
Stage #1
Gas Nitrogen
Pressure Bar
Training period days
Training results - Dark current is rising up/down from to 6A at HV=5200V.
It was fixed the number of anode wire which are associated with this current.
Conclusion: take out TPC from the vessel to see
what happened.

14. Results of the TPC#2 electrodes
visual inspection
1.No traces of dust.
2.No dark spots on the anode.
3.One dark spot (3mm diameter) has been observed on the cathode (top) directly in front of labeled anode wire .
Date of start – 6 April 2004
(One week later)
Gas - Nitrogen, 5 Bar
Test duration - One week
Stage #2
HV=5400V HV=6300V
Neighbor wire  A  A
Central wire 2.5 A 3.0 A
Neighbor wire 2.2 A 3.0 A

15. Currant from central wire
Total currant
Currant from central wire
Nitrogen. 5 Bar.

16. Stage #3 Conclusion: take out TPC from the vessel to see
Gas - Hydrogen. 10 Bar
Date of start – 14 April 2004
Testing period - 7 days
Obtained results.
1. TPC is running more unstable. First trip (10A) was at HV=4700V.
2. Current in hydrogen exceeds current in nitrogen by 2-3 times.
3. Dark current is about 20A at HV=6200V.
Conclusion: take out TPC from the vessel to see
what happened again.

17. Results of the TPC#2 electrodes
visual inspection
1.No traces of dust.
2.No dark spots on the anode.
3.Three dark spots have been observed on the cathodes.
3.1. Two of them are placed symmetrically with respect each other directly in front of labeled anode wires.
3.2. Diameter of top (cathode) spot increased up to about 12mm.
3.3. Diameter of bottom (strip-cathode) spot was about 7mm.
3.4. Third spot had diameter about 3mm and placed far away from mentioned above sports.

18. Element distribution along the hot spot that are placed on the cathode wires
Strip-cathode
Cathode

19. 90Sr source has been collimated
Actions
1. Cathode wires with spots have been replaced by new one.
2. TPC was assembled again.
3. Hydrogen. 10 Bar.
4. Date of start – 4 June 2004
5.Testing period months
(till now)
6. Main cathode - HV = 25 kV
Stage #4
90Sr
90Sr source has been collimated

20. After taking out of cathode wires with two hot spots the dark current behavior improved significantly.
So, the point where dark current is rising up more than 100 times has been shifted from HV=4.7kV to about 5.8kV.

26. Summary
We feel ourselves quite optimistic because the life become more better.
At the moment we have quite good experimental facilities to perform the TPC study at PNPI. We can work with two TPC simultaneously and we do it.
2. Working characteristics of TPC#1 and TPC#2 looks quite promising. Our goal is to investigate TPC behavior, including extremely high working conditions. TPC must be reliable working device.
3. It is necessary to investigate the nature of dark spots on the cathodes and prevent their creation.
4. We are going to start production of TPC#3 and TPC#4 only after finishing of TPC#1 and TPC#2 investigations.
5. We believe that at least one of these TPC will work in the next our beam run at PSI.