1. BLM internal review M.Hodgson 17.02.04
Gain Variation in SPS Ionisation Chambers
Current Data:-
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

2. BLM internal review M.Hodgson 17.02.04
Gain Variation in SPS Ionisation Chambers
Current Data:-
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

3. 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 BA (replaced 2003), - 23 and (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

4. 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 BA ) 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

5. 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
Modified
BLM internal review M.Hodgson

6. BLM internal review M.Hodgson 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 vs Voltage To find the optimal operating voltage and to check the voltage dependent ionisation properties (a).
Signal
(a)
(b)
(c)
- 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. V
- 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

7. 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