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NEW Ionization Chamber Technology

NEW Ionization Chamber Technology. Anne Dabrowski Results on behalf of Mayda Velasco’s Hardware Research group . P. Ball 3 , A. Darowski 1 , G. Graham 3 , C. Kendziora 2 , F. Krueger 2 G. Tassotto 2 , G. Ünel 1 , M. Velasco 1

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NEW Ionization Chamber Technology

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  1. NEW Ionization Chamber Technology Anne Dabrowski Results on behalf of Mayda Velasco’s Hardware Research group. P. Ball 3, A. Darowski 1, G. Graham 3, C. Kendziora 2, F. Krueger 2 G. Tassotto 2,G. Ünel 1, M. Velasco 1 1 Northwestern University,2 Fermilab,3 Richardson Electronics Lunch Bag Seminar 1 May 2002

  2. Why the need for new Hardware? • Modern High Energy Experiments • High intensity beams > 1011 particles/ micro second • Radiation Hard • Once-off calibration • Monitor beam line position / background particle flux Northwestern High Energy Physics

  3. Solution: • Ceramic radiation hard ionization chambers. • Either Gas sealed or Vacuum – SEM (secondary emission monitor) • Q = I * d * e*A * n * M current read by chamber M – multiplication factor (~1) N – tot num of ion/electron pair/cm (8 for He at atm 98 for Ar at 1 atm) A – elecrode area (cm2) (1 cm2) I – beam intensity (cm-2 s-1) (<1011 cm-2 s-6) d – gap size (cm) (~1mm) e – electron charge Northwestern High Energy Physics

  4. Basic Description of Design Northwestern High Energy Physics

  5. Basic Chamber Design Northwestern High Energy Physics

  6. Engineering drawing • Tolerances: • Gap = 1mm +/- 0.001” • guard-to-collector = 0.5 mm+/- 0.002” • Flatness 0.001” Northwestern High Energy Physics

  7. SIC prototypes Northwestern High Energy Physics

  8. Timeline for Design Development • 2000 Richardson Electronics (REL) made Glass Chambers (Inspired by V. Falaleev Design). • Detection observed • Design studies • Change to ceramic because of high tolerances • Ceramic design • Electrode changed from round edges to edges square D1 – D2 • Flat for signal collector & guard ring. • Multiple chambers produced (7 in all) • gas refilling tested. • Found occasional shorts on due to metal filings inside the chamber…tooling redesign. • Believe have the final design • (testing by producing several chambers….already under construction). • successful • mass production will start at the rate of 10 chambers/week. Northwestern High Energy Physics

  9. How do they Behave ? Northwestern High Energy Physics

  10. Radiation Physics Calibration Facility (RPCF)Photon Emission 424 R/hr • Check chamber quality • Plateau, ionization response, reproducibility • Lead to design improvements • Determined operational modes • operational voltage, gain voltage, gas type • Do pre-calibration before operating in other facilities. Northwestern High Energy Physics

  11. Radiation Physics Calibration Facility (RPCF,FNAL) “Flat mounting” • Two new Cs137 sources: • Max:1600 Rad/Hr • The old source was • 424 Rad/Hr “Side Mounting” Northwestern High Energy Physics

  12. Results (RPCF) Note Slope !! Electrode edges Northwestern High Energy Physics

  13. What Changed?Design 1 vs. Design 2 The electrode edge … Curved Flat Effected slope of plateau … reduced by ~ 70 % Northwestern High Energy Physics

  14. Signal > Electrode area Results D2 vs. D4 Northwestern High Energy Physics

  15. Setup to test chambers at the RPCF– pre-calibration for all SICs • Investments: A Keithly • electrometer • Sensitivity 2 nC • Resolution of 0.1 pC • Bias current of < 3fA • Output of electrometer via GPIB to computer running LabView to a data file. • Procedure almost automatic  Good for grad students when calibrating in the summer  Northwestern High Energy Physics

  16. Chamber Characterization show no radiation damage after XX protons Chamber filled with He for more than a year Reproduce calibrations No change… Northwestern High Energy Physics

  17. Summary of RPCF Results: • Good reproducibility • Can measure both small and large currents. • Keithley Electrometers and Powers Supplies allows to do good measurements of knee of plateau need to test gas quality of chambers… no degradation see so far. • LABview DAQ – user enter customized measurement parameters – automated DAQ • Slopes good – but not quite flat… we believe we understand it.

  18. Tests at ATF (BNL) low energy electron beam No saturation below 8*109/p/cm2 Northwestern High Energy Physics

  19. Booster (FNAL) proton source ~1e9 to 1e12 1mm Wire Chamber & SIC SIC Only New Toroid +chamber for Flux measurement & Longitudinal movement for alignment Old Toroid only for Flux measurement

  20. Booster (FNAL) HaloHigh intensity ~ 1e9 proton source1.5 ms per spill … halo see 1/100 of total beam ONLINE OFFLINE

  21. Booster (FNAL) Plateau in the beam (1.8e11)---saturation (same effects present with design 4) shortens plateau—space charge Northwestern High Energy Physics

  22. Booster (FNAL) – Intensity Scan SEM-like SIC-like Clear … Saturation No saturation even At 1012 ppp (10-5 torr) Northwestern High Energy Physics

  23. Beam Profile from Wire chamber Need to repeat With vertical movement Beam Moved Chamber see about 40% Of the beam Northwestern High Energy Physics

  24. Summary of results from Booster • Saturate above e11 in SIC-mode, but no saturation in SEM-mode. • When making plateaus: gain observed at 200 V in the beam center, but not seen at 350 V in the “halo” like in the RPCF tests • use SWIC electronics for both low and high currents just change capacitors • So far no signs of radiation damage … or helium leakage • To do… add vertical movement to get proper alignment. Northwestern High Energy Physics

  25. Secondary Emission Monitor– SIC chamber in vacuum • Getter - Place a strip of barium under the collector and activate it at about 1000 degree C. • Ion Bombardment - Apply a voltage across the electrodes while pumping for reducing atmosphere of H2. • Richardson used this process on vacuum tubes to 10-8 torr This look like a very promising way of operating The chambers for >1011 ppp Northwestern High Energy Physics

  26. Permeation Test– test run for 3-4 days … Helium is not leaking…. • The ion chamber was then put in side of a small vacuum chamber and tested using a Dupont Mass Spectrometer leak detector the total leak rate was found to less than 2X10 –10 STD CC P/S. • Then the temperature was raised slowly to 100 degree C. • Max leak rate < 40X10 –10 STD CC P/S Northwestern High Energy Physics

  27. Conclusion Northwestern High Energy Physics

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