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EM background tests of IP feedback hardware

EM background tests of IP feedback hardware. Christine Clarke Oxford University 24 th September 2007. Oxford (P. Burrows, C. Perry, G. Christian, T. Hartin, H. Dabiri Khah, C. Clarke, C. Swinson, B. Constance) Daresbury (A. Kalinin) SLAC (Mike Woods, Ray Arnold, Steve Smith) KEK.

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EM background tests of IP feedback hardware

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  1. EM background tests of IP feedback hardware Christine Clarke Oxford University 24th September 2007 • Oxford (P. Burrows, C. Perry, G. Christian, T. Hartin, H. Dabiri Khah, C. Clarke, C. Swinson, B. Constance) • Daresbury (A. Kalinin) • SLAC (Mike Woods, Ray Arnold, Steve Smith) • KEK

  2. FONT at ESA: The ILC Environment • The IP feedback BPM sits between the Beam Calorimeter and the first extraction line quad. • This area has lots of low energy particles due to interaction of e+e- pairs and photons (from beam-beam interaction) with IR material. Low-Z mask Beam Cal IP Feedback BPM Extraction Quad C.I.Clarke

  3. FONT at ESA: Hits on striplines • GEANT3 Simulations by Tony Hartin (Oxford) show up to 105 particle hits per stripline • Are simulations correct down to low energies? • Charges being added or removed from the BPM causes errors (1pm per charge – Steve Smith). • FONT requires resolution on the micron level. C.I.Clarke

  4. FONT at ESA: Module • Recreate the environment around the BPM • (Match the particles entering the region) • Match the materials in the region • Constructed at Daresbury. Low Z Mask Beam Cal Stripline BPM Quad Pole face C.I.Clarke

  5. FONT at ESA: Requirements All charges at the ILC • ILC conditions impossible to replicate but we can identify the parts that matter- energies and fluxes of particles that cause hits on BPM striplines. • We require electrons and positrons of average 4 GeV impacting front face of module as well as the original electron beam. Low Z Mask Charges that go on to cause hits on striplines The charges that cause hits on the striplines peak around 4 GeV C.I.Clarke

  6. FONT at ESA: Method 1 • Ran tests at End Station A (ESA) at SLAC. • Scanned the electron beam across the front face of the module. • CCD camera to aid positioning beam spot on the front face of the module. • A Low Flux Toroid monitored beam charge down to 106 electrons. • Ran at 28.5 GeV, ~107 electrons beam charge. Produced ~15000 times more hits per stripline than worst case ILC. C.I.Clarke

  7. FONT at ESA: Method 1 Results • Signals with the beam on the Low Z mask were different from BPM stripline signal- suggestive of secondary emission. • The signals caused by secondary emission were not large enough to cause problems for the operation of the IP BPM. C.I.Clarke

  8. FONT at ESA: Method 1 Simulations • Simulating these results in GEANT has had some success (Tony Hartin). • Normal stripline response + Secondary emission C.I.Clarke Simulation (T. Hartin) Real Data from ESA

  9. Energy spectra from Aluminium Radiators and ILC charges Energy spectra of charges hitting BPM striplines for ILC and ESA proposal FONT at ESA: Method 2 • Second method delivers both electrons and positrons as a halo around the main electron beam using thin radiators just upstream of module. • The energies of charges hitting the module do not match. • GEANT simulations show this does not affect the energy distribution of what hits the striplines. • Can make numbers match. C.I.Clarke

  10. 28.5 GeV e-beam FONT at ESA: Method 2 • 3 aluminium foils used, 1%, 3%, 5% X0. • Recorded 1000 stripline signals without foils. • Recorded 1000 stripline signals with foils. • With 5% X0 foil in, Produced ~5000 times more hits per stripline than worst case ILC. C.I.Clarke

  11. FONT at ESA: Method 2 Results • No change with foil in and foil out. • Statistical errors on parameters (d and z) greater than the difference between the foils in and out. • Statistical error is 700 times smaller than the value that constitutes a 1 micron error in position measurement at the ILC. A d = (A+B)/(A-B) z = C/(A-B) C B C.I.Clarke

  12. FONT: Summary • IP Feedback BPM sits in a region where backgrounds are present. • Created backgrounds and recorded stripline behaviour. • Stripline signal shows secondary emission. • Some success in understanding the exact form just using GEANT3. • Signal is not large enough to cause problems with micron-level position measurement at the ILC. • General • Ability to simulate IR backgrounds. • Other beamline elements can be tested there. C.I.Clarke

  13. C.I.Clarke

  14. FONT at ESA: Method 3 (no plans to use this method) • To match energies and fluxes, we propose Be target in BSY. • We can select only 4 GeV electrons. • We can fill the entire beampipe with electrons so illuminating the whole front face of the module. Collimators and optics control the shape. • We can change fluxes to match ILC backgrounds or to make them a factor of ten worse. • We only have spray- no primary beam to measure. C.I.Clarke

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