Transcript SPS measurements on installed chambers, gain variation - AB-BDI-BL

Gain Variation in SPS Ionisation Chambers
Current Data:-
Chamber Tests - 2003/2004
50
y = -0.0019x + 45.722
(2003 SPS Tunnel Test Averages)
Gain/ pA
45
y = -0.0045x + 43.969
(2004 Lab Tests on new chambers)
40
y = -0.0105x + 43.512
35
30
25
4
5
6
Chamber #
or
BA section
Repaired, Air
Filled
3
Repaired, Air
Filled
Repaired, Air
Filled
2
Damaged, N 2
Filled
1
Lab Chamber
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56
Results: - Difference in current between tunnel tests and laboratory (about 4%)
- Slight variation between either gas or pressure (New chambers 1.1atm, air STP)
- Problem with removed N2 filled chamber.
BLM internal review
M.Hodgson
17.02.04
Gain Variation in SPS Ionisation Chambers
Current Data:20
18
16
14
12
10
8
6
4
2
0
160
Extr., inj. BLMs
Ring BLMs
140
120
100
80
60
40
20
0
60
66 More
M
or
e
54
66
48
60
42
54
36
48
36
30
42
Frequency distribution
SPS Ionisation Chambers 2003
current [pA]
Results:
- In SPS ring, main distribution at 45 (+ 3) pA
- In SPS INJ/EXT points large amount of variation around the main distribution
of 45 (+ 3) pA, possibly from remnant radiation or radioactively induced chamber
material alteration.
BLM internal review
M.Hodgson
17.02.04
Gain Variation in SPS Ionisation Chambers
To do:- Re-inspection of installed chambers
The chambers in INJ/EXT lines of the SPS to be re-tested at installation points and away
from installation points.
By testing away from possible radioactive areas evidence of remnant radiation may become
apparent
Re-inspection of chambers at SPS BA5 - 18 (replaced 2003), - 23 and - 30 (away from
main distribution of 2003 results).
If variation remains there could be problem with area or equipment
- Radiation inspection
Check chambers to see if radioactive
When exposed to radiation for long periods it is possible chambers may become
radioactive themselves, hence affecting the gain
- Removal
Chambers 23, 30 from SPS BA5, several working chambers and several from INJ/EXT
points will be removed for inspection.
Chambers will be required for laboratory tests and comparison
BLM internal review
M.Hodgson
17.02.04
Gain Variation in SPS Ionisation Chambers
- Gas and material inspection
The gas and material, of the chambers removed (and the damaged N2 filled chamber,
formerly BA5 - 18 ) shall be inspected with a mass spectrometer.
Constant and long term irradiation may cause material properties to change
- Gas investigation
Chambers will be refilled and re-tested with varieties of gases and pressures
Certain gases or combinations may provide a better or more reliable gain
- Simulation
Simulations of the shower particles passing through the ICs will be conducted using Geant
To provide a model of what happens within the chambers
- Signal vs Voltage inspection
All chambers removed and installed will have there signal – voltage relationship
investigated
May show how the ionisation properties of the chambers alter over lifetime
- Accelerated Lifetime investigation
Chambers to be installed near N EXT and constantly inspected, for gain and radiation dose,
during 2004 running period
May be able to show how the gain varies with exposure and hence provided an
estimation of a chambers lifetime
BLM internal review
M.Hodgson
17.02.04
Gain Variation in SPS Ionisation Chambers
Tests conducted for the design of an improved ion chamber for the SNS,
by simply altering the
connection to the electrode and
removing the sharp edge the
results show a better long
straight section and ionisation
properties (below).
Unmodified
Modified
It is therefore apparent that
small modifications can
cause significant changes to
the properties of the
ionisation chambers.
Unmodified
BLM internal review
M.Hodgson
Modified
17.02.04
Forthcoming tests on the 5 LHC prototype ionisation chambers:
- Gain Tested
Each IC to be tested with Cs 137 source in laboratory.
Signal
- Signal vs Voltage
To find the optimal operating voltage and to check the
voltage dependent ionisation properties (a).
(a)
(b)
(c)
V
- Installation
One chamber installed in both BA2 (near extraction) & BA5 (near new
collimation) of the SPS for 2004 running period. Signal and long term
radiation affects to be compared with current chambers, which are also
positioned in these test areas.
- Extraction and Investigation
Removed from SPS and re-tested (Gain and Signal vs Voltage).
- Gas Inspection
Gas removed and inspected in mass-spectrometer.
BLM internal review
M.Hodgson
17.02.04
An investigation is also to be carried out into the design of the
chambers to make sure that the design is the most efficient and cost
effective, however this may require chambers manufactured with
different design features. To be investigated:
• cleaning methods
• outgasing
• gas composition and purities
• leak tests.
Further tests may also need to be carried out depending on the
outcome of the investigation into the current ionisation
chambers. This may include accelerated life/high radiation
exposure tests.
BLM internal review
M.Hodgson
17.02.04