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 17.02.04

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 17.02.04

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

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

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 17.02.04

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 17.02.04

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