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TEVATRON IONIZATION PROFILE MONITOR

TEVATRON IONIZATION PROFILE MONITOR. Andreas Jansson Fermilab. AD: B. Dysert C. Lundberg C. Rivetta L. Valerio J. Zagel …. CD: M. Bowden R. Kwarciany D. Slimmer. People. PD: K. Bowie A. Bross T. Fitzpatrick H. Nguyen.

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TEVATRON IONIZATION PROFILE MONITOR

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  1. TEVATRON IONIZATION PROFILE MONITOR Andreas Jansson Fermilab

  2. AD: B. Dysert C. Lundberg C. Rivetta L. Valerio J. Zagel … CD: M. Bowden R. Kwarciany D. Slimmer People PD: K. Bowie A. Bross T. Fitzpatrick H. Nguyen Also help from: T. Anderson (AD), H. Glass (TD), D. Harding (TD), B. Hively (AD), V. Kashikin (TD), D. Miller (AD), Z. Tang (PD), Jim Volk (AD), T. Zimmerman (PD), the Tev Techsand anyone I may have missed. Tevatron Ionization Profile Monitor

  3. Talk outline • Motivation for IPMs in Tevatron • Special challenges in Tevatron • Design of Tevatron IPMs • Various tests • Pictures from “down under”. Tevatron Ionization Profile Monitor

  4. Motivation • Directly measure injection matching and emittance growth at injection • Turn-by-turn at 10% beam size resolution • Continuously measure emittance eg on ramp • Average at ~% beam size resolution Tevatron Ionization Profile Monitor

  5. IPM working principle • Measure distribution of rest gas ionization by: • Drifting ions onto a detector using an electric field, or • Drifting ionization electrons onto a detector using a E||B field. Tevatron Ionization Profile Monitor

  6. Challenge I – Small beam size • Small beam size -> fine detector granularity (1/4 mm pitch) • Three different positions due to helix -> need wide active area (~3 cm) • Many channels (128) Tevatron Ionization Profile Monitor

  7. Challenge II – Two beams Y [mm] Inj. old helix • Projected beam profiles may overlap • Don’t trust to separate beams • Separate by timing -> single bunch resolution! Inj. new helix Flattop X [mm]  = 20  mm mrad p/p = 7.5 10-4 One and three sigma contours Tevatron Ionization Profile Monitor

  8. Challenge III – Too good vaccum graph: F. Sauli, CERN 77-09 • Gas pressure at E0 before 2004 shutdown was in low 10-8’s, slated to be improved • Based on estimated gas composition (RGA scan), expect about 1000e/bunch for a 10cm detector at 3 108 Torr and 2.7 1011 protons/bunch. • Need for a local vacuum bump after vacuum inprovements. Tevatron Ionization Profile Monitor

  9. Challenge IV – Parasitic signals dB • Measure extremely small signal (~fC) in the presence of very strong EM field from beam. • Anode strip acts as electrostatic pick-up. • Sharp resonaces require strong LP filtering, which limits time resolution. Hz beam-to-anode strip coupling measured on Booster IPM. Tevatron Ionization Profile Monitor

  10. Fermilab QIE8 ASIC • Charge Integrating Encoder (QIE) • Developed at Fermilab • Used by KTeV, CDF, Minos, CMS… • Frequency range 7-53 MHz • No deadtime. • LSB 2.6fC (16000e) in logarithmic mode, 0.9fC (6000e) in linear mode • Dynamic range >104 in logarithmic mode • Can achieve noise of O(1fC) • Radiation “tolerant” design: T. Zimmerman Tevatron Ionization Profile Monitor

  11. QIE simulations • Injection is most difficult (fewer counts per channel). • Signal per bunch is small, but gain limited by MCP saturation effects from total (proton) signal. • Need about 300 primaries (per bunch) for 10% beam width accuracy (requires gas injection). • Higher accuracy can be obtained by averaging many turns (ramp measurement). simulations: H. Nguyen Tevatron Ionization Profile Monitor

  12. Keeping the noise low • To keep noise at minimum, digitize close to source (in tunnel). • 128 channels  1 byte  15 MHz = 16 Gbit/s of data! • Use high-speed serial links (on optical fiber) Tevatron Ionization Profile Monitor

  13. QIE test stand measurement: H. Nguyen • Using laser based PMT test setup in Lab 6 • KTeV test board modified with CMS-QIE • Observed good linearity and insensitivity to clock phase Tevatron Ionization Profile Monitor

  14. QIE quirks • QIE input is NOT bipolar! • Relatively small pulse of wrong polarity can temporarily shut down the QIE input • Beam EM pick-up generate bipolar pulses • Cable reflections may invert pulse polarity • Limit diffuse, need to be careful with signals example of pulse induced by beam EM Tevatron Ionization Profile Monitor

  15. Cable tests • Stepping QIE clock phase w.r.t the incoming pulse, can improve time resolution • Derivation of composite signal yields the original pulse • Used to study reflections due to connectors in front-end cabling x30ns x30ns measurement: C. Rivetta Tevatron Ionization Profile Monitor

  16. Rad level measurements • Reading 125 mrad/h average at ~4.5 feet during normal running • 18 years to 20 krad! Tevatron Ionization Profile Monitor

  17. Component rad tests • Tested commercial TI serializer in Tevatron tunnel for >200 days. • Previously tested (by others) for total dose ~Mrad. • Only handful of link errors seen. • One latchup candidate, cleared by cycling power. • Observed error rate should not affect operation. Tevatron Ionization Profile Monitor

  18. Microchannel plate saturation Turn # • MCP output current per unit area is limited by MCP pore recharge time. • If hit rate per pore exceeds recharge time, output is reduced • Onset of saturation observed in MI IPMs, as expected from calculations. • For Tev, will abandon Chevron configuration since extra gain can not be utilized (allows to run at higher bias). measurement: L. Short Bull Tevatron Ionization Profile Monitor

  19. MCP test stand photo: A. Bross • Built to measure eg gain depletion of used MCPs, and as a test bed for new systems (eg Tev IPM). measurement: B Dysert Tevatron Ionization Profile Monitor

  20. Detector design • Based on MI eIPM prototype • Flange-mounted detector for quick installation • Many modifications • Better screening • Different voltage profile • Provisions for calibration device Tevatron Ionization Profile Monitor

  21. Beam EM screening 10kV MI, Booster • Enclose anode board and signal cabling in Faraday cage! • Wire mesh over MCP lets (most) electrons thru • Avoid signal cable mismatch as far as possible 1kV GND 10kV Tev 1kV GND Tevatron Ionization Profile Monitor

  22. Anode board artwork: C. Lundberg • ¼ mm strip pitch • 200 channels (128 instrumented) • Provision for on-board LP filter/ back-termination (series resistor) • Connected to feedtru by UHV compatible 50Ω flex-circuits • High resolution area can be moved by swapping connectors Tevatron Ionization Profile Monitor

  23. Beam based alignment beam • Due to high strip aspect ratio (400:1), good alignment with beam is required. • Motorized detector stands allows for beam-based elimination of any relative angle (by minimizing measured beam size) • Translation is also possible, to scan active area on MCP anode strips graph: K. O’Brien Tevatron Ionization Profile Monitor

  24. Internal calibration “hot wire” • Internal electron source (hot wire) to illuminate the MCP with electrons • Track changes in MCP gain Tevatron Ionization Profile Monitor

  25. Tevatron OTR Detector Tevatron OTR Detector • Use off-the-shelf camera and optics to measure OTR light produced by thin foil in beamline • 2D beam profile measurement • Thin foils (few mm hydrocarbon + 0.1 mm AL) • Three foil position design • Proton foil, pbar foil and no foil • Measure beam in both directions • Rad-hard 30 frames per second camera Will be used for absolute calibration of IPMs Slide from V Scarpine Optics/Camera Tower Foil Motion Driver Vacuum Can 4” Beam Aperture Tevatron Ionization Profile Monitor

  26. Magnets • Single corrector (two-bump) for simplicity. • 0.2T electromagnets chosen. • Can be turned off to verify effect on measurement and machine. • Bought from outside manufacturer. design & photo: Scanditronix Magnet Tevatron Ionization Profile Monitor

  27. Tracking – transverse displacement • Ionization electrons simulated in B=0.2T, E=100kV/m. • Transverse spread from electron momentum less than ¼mm pitch • Small space-charge effect seen for protons at flat-top. Tevatron Ionization Profile Monitor

  28. Field quality • Longitudinally, E-field is not perfect • E×B component produces a small transverse drift velocity • To first order, this generates a rotation of the beam “image”, which is removed by beam-based alignment • Higher order terms distort the beam image, expect order ~30 nm rms effect on beam size. Tevatron Ionization Profile Monitor

  29. Field quality - observations • S-shape of discoloration on MI eIPM probably due to field distortions photo: J Zagel Tevatron Ionization Profile Monitor

  30. sector valve Differential pumping scheme Calibrated leak N2 shut-off valve gauge ion pump ion pump ion pump ion pump ion pump sector valve sector valve orifice gauge vert ipm horz ipm TSP TSP ion pump ion pump ion pump Tevatron Ionization Profile Monitor

  31. Simulated pressure profile simulation: A. Chen • Opening leak valve raises pressure by two orders of magnitude. Tevatron Ionization Profile Monitor

  32. 3 decades 6 hours Controlled N2 leak tests at E4R leak on test setup: S. McCormick Red traces: IP and IG in leak chamber Green, Blue and Cyan: IPs and IG in main chamber Tevatron Ionization Profile Monitor

  33. DAQ system • CMS-QIE front end in tunnel. • Serial data uplink on optical fiber • Receiver and data buffer in upstairs PC • Timing + clock + QIE settings supplied from PC thru cat-5E cable Host PC (LabView) Data Buffer (2*8 ch) (PCI) Timing card (PCI) Timing fanout QIE cards (16x 8 ch) Tevatron Ionization Profile Monitor

  34. Timing card • Produces the 15MHz (2/7 RF) FE clock • Decodes and transmits beamsync clock (p & pbar) injection events • Transmits QIE settings • Separate version of card will decode TCLK/MDAT design & photos: T. Fitzpatrick Tevatron Ionization Profile Monitor

  35. Timing scheme 396 ns (21 buckets) p-pbar separation ~120ns RF 2/7 1/7 Tevatron Ionization Profile Monitor

  36. Front end card design & photos: K. Bowie • 8 channels (CMS QIE) per board. • Data is serialized by CERN GOL ASIC (rad hard) and sent thru fiber • Timing fanout board cleans up and distributes clock and timing signals QIE card timing fanout Tevatron Ionization Profile Monitor

  37. Data buffer card • Handles 8 incoming optical channels • Data stored in on-board RAM • Read out thru 64 bit PCI bus • Doubles as BTeV L1 data buffer prototype. design & photo: R. Kwarciany Tevatron Ionization Profile Monitor

  38. DAQ status • System test setup in Lab 6 • Currently debugging hardware • Will move to inject signals with laser-PMT system Tevatron Ionization Profile Monitor

  39. Tunnel installation Magnets, stands, vacuum chambers, pumps, cables, plumbing in place! Detector goes here! Tevatron Ionization Profile Monitor

  40. Conclusions and outlook • Tevatron IPM project is making progress • All infrastructure installed this shutdown • Detector unfortunately not ready to be installed • Can make use of a few days downtime to install detector and electronics. Installation of MI eIPM (similar modular design) Tevatron Ionization Profile Monitor

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