Conditioning tests

1
Reconditioning Tests for Separator 20

• Conditioning tests
• Separator history
• Conditioning at 150 180 kV
• Dark currents
• Spark rate at 170 kV
• Radiation scans
• Summary

2
Measurement Scheme
3
Separator History

• Separator 20
• Separator (vertical) with hand-polished SS
  plates was constructed in 1990?
• Removed from Tevatron in March 2006
• Reassembled and cleaned in June 2006
  (mounted 2 new HV feedthrus)
• Reconditioned at voltages up to 180 kV in
  June - July, 2006 at MP-9

4
Conditioning at 150 kV (June 6-7, 2006)
Negative Polarity
Positive Polarity
15 sparks
100 sparks
5
Radiation scan at 150 kV (June 7, 2006)
Hot spot
Microdischarges
6
Conditioning at 170 kV (June 7, 2006)
Positive Polarity
Negative Polarity
Voltage drop
High current
40 sparks
20 sparks
Problems - no current drop for about 8
hours - voltage is limited by current limits
(100 mA)
7
Conditioning at 160 - 170 kV (June 8 - 9, 2006)
Positive Polarity
30 sparks
20 sparks
June 8
June 9
8
Conditioning at 170 - 180 kV (June 10 - 11, 2006)
Negative Polarity (June 10-11)
Positive Polarity (June 10)
220 sparks
80 sparks
9
Radiation scan at 165 kV (June 11, 2006)
Hot spot
10
Spark Rate Measurements
Negative Polarity
Positive Polarity
11
Radiation scan at 165 kV (July 12, 2006)
Hot spots
Hot spots
Radiation hot spots are suited in the central
separator area for both polarities
12
Dark Current Measurements
After conditioning at 150 kV
After conditioning at 180 kV
After conditioning at 180 kV a current has
dropped for negative polarity at 150 kV from 40
mA to 5 mA
Dark current after shut down (June 15 - 28)
Final dark currents (2 weeks conditioning at 170
kV)
Current at 170 kV is about 30 mA for both
polarities
13
Spark Rate Measurements
Spark rate at 170 kV 1.5 sparks/day
for negative polarity 2.5 sparks/day for
positive polarity Estimated spark rate at 150
kV 10 sparks/year for both
polarities
14
Summary

• The results of conditioning tests (June 6 July
  12, 2006)
• The separator 20 removed from Tevatron was
  reconditioned at voltages up to 180 kV
• for both polarities. The higher
  conditioning voltages helped to eliminate a high
  corona
• current observed at 150 kV and improve
  spark rate parameters.
• Parameters at 170 kV
• - dark current is 30 mA (not
  change for about one month)
• - spark rate is about 2.5
  spark/day for both polarities
• Separator parameters at 150 kV
• - dark current is about 8 mA
• - estimated spark rate is about 10
  sparks/year
• Radiation scans carried out a few times have
  detected hot spots in the central area.
• No vacuum leak was detected before starting
  of the conditioning tests but we could not
• reach vacuum better than 10 -9 torr. A
  separator was opened and stored for long time
• without HV feedthrus so we need to bake
  out before operation at Tevatron.