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Status of e-gas studies

U. Koetz 16.01.03. Status of e-gas studies. V.Andreev, R. Stamen, T. Haas , U.Koetz, C. Niebuhr. Comparison of simulations: H1 and ZEUS Comparison with experiments (calorimter) Studies for C5A collimator Proposal to improve vacuum upstream (GA) Status of e + / e - simulations

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Status of e-gas studies

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  1. U. Koetz 16.01.03 Status of e-gas studies V.Andreev, R. Stamen, T. Haas, U.Koetz, C. Niebuhr Comparison of simulations: H1 and ZEUS Comparison with experiments (calorimter) Studies for C5A collimator Proposal to improve vacuum upstream (GA) Status of e+ / e- simulations Conclusion thanks to K. Klimek and G. Kramberger

  2. Blue lines: Photons > 100 keV Red Lines: Electrons > 100 keV Positron hitting C5A

  3. H1 vs. ZEUS Simulation • ZEUS: • Bremsstrahlung with 1/k spectrum • Neglect: • photon • Positron scattering angle (now full e Z ->e’ Z  with angles from Lumi-MC) • Use transport-type simulation from 132 – 2m • Feed into full GEANT at Z=2m • H1 • Bethe-Heitler cross section • Full beam line up to 60m • Track positron and photon (and any secondaries from secondary interactions

  4. Production angles still to be compared !

  5. Low energy tail due to tertiary particles from shower development ??

  6. H1 comparison with experiment Experimental data simulation Spacal hits Spacal energy hits in CJC

  7. Using H1 and ZEUS 4-vectors in ZEUS GEANT

  8. ZEUS RCAL data and simulation

  9. Studies for C5A Collimators at ~ 80 cm downstream of IP 19 mm for e- H1 ZEUS 19 mm for e- 11.5 mm for e+ 11.5 mm e+ 66 mm 26 mm 89 mm 87 mm 129 mm 110 mm ~ 20 mm thick W ~ 45 mm thick W In case of ZEUS C5A contributes to CTD current and doses to MVD more than necessary make C5A as thin as needed for absorption of SR In case of H1 C5A reachable only when beampipe is taken out

  10. Shields against back scattering of SR from C5A into drift chamber 0.4 cm Optimised for HOM?

  11. 27m 32 m Improvement of vacuum upstream of IP improvement of vacuum will reduce driftchamber currents trigger rates doses to detectors and readout of MVD Pressure nmb between 32 and 25 m in front of IP vacuum chamber inside proton magnet GA no getter or NEG pump Vacuum simulation show large increase of pressure assume local pressure bump of x5 over mean

  12. Factor 5 Bump:  Rate: Factor 1.5

  13. R2 R3 R4 towards center Radmon diodes in similar arrangement R1 leakage current increased a similar plot exists for noise increase Ileak ~ 2 A in 2002 noise increase up to 5% (max 9%)

  14. Runs over ~ 10 hours with with Ie+ between 30 and 10 mA within the resolution of the radfets (200 rad/bin) constant over the run under current conditions doses dominated by injection inefficiency and beam losses

  15. Currents still far from nominal values of 58 mA earlier estimates based on egas MC for 60 mA e- and p ~ 2 10-9 mb and 107sec/year 100 krad in horizontal plane observation on radmon diode show similar asymmetry like radfets current in radmon 15 after optimisation( inner horizontal like R1 radfet) ~1nA corresponding to 5 mrad/sec for beam of ~20-30 mA 10 hour run @25 mA 200 rad 1 year of 107 sec and 60 mA 120 krad CMOS electronics tolerates ~ 300 krad dosimeters further downstream than MVD normalisation of dosimeters with respect to MVD still to be done Even if currently inefficiencies and accidents are dominating which we hope can be brought under control soon any improvement of upstream vacuum is very valuable

  16. Comparison of e+ against e- GeV GeV e+ e- optic file from end 1998 m m since for e- distance to C5A is larger by 8 mm rate of losses on C5A and beampipe smaller than e+ case rate of e- about factor 2 smaller than for e+

  17. Things to be done vacuum studies around GA magnet studies for Coulomb scattering? Experiment with largely increased gas density at Hermes did not show big effect but behaviour of vertical collimator at 6m not understood effects of rotators to be studied since according to simulations there is no sensitivity to egas for > 80 m one could expect no large effects from the rotators from e-gas point of view ZEUS will modify the C5A collimator ZEUS asks for improving upstream vacuum in particular around GA magnet

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