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Extinction

MECO Collaboration Meeting 6 February 2005 Yannis Semertzidis BNL. Extinction. Goals, MECO note #140r Modes of Operation at AGS and their impact Measuring 10 -9 extinction at AGS: a) E-O effect b) -rays Monitoring extinction outside the AGS ring Neutrons Comment on note 138.

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Extinction

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  1. MECO Collaboration Meeting 6 February 2005 Yannis Semertzidis BNL Extinction • Goals, MECO note #140r • Modes of Operation at AGS and their impact • Measuring 10-9extinction at AGS: • a) E-O effect • b) -rays • Monitoring extinction outside the AGS ring • Neutrons • Comment on note 138

  2. Extinction Related Backgrounds

  3. General Extinction Plan • Minimize Extinction at the AGS 1) Optimize operation mode (1 or 2 bunches, etc.) 2) Monitor it at AGS • Enhance it (Insurance Policy) and Monitor it at Extraction

  4. MECO beam structure: MECO experiment

  5. 1.35 s What is Planned for the AGS Ring Mike Brennan (1998) • Use a 60KHz AC Dipole Magnet (CW). Resonance at the vertical betatron frequency • Use a pulsed Strip-line kicker to kick the full buckets into stable orbits. • Need 1-50ms to drive particles off (driven by the strip-line kicker)

  6. Required Extinction vs Time (MECO note #140r by BM, YS)

  7. Buckets at AGS with h=6, W. Glenn Buckets are connected creating unstable fixed points to which our planned (RFFM- sinewave) monitor is not sensitive.

  8. One or Two filled buckets? (W.Glenn) • At Injection the proton phase space is large (scales as 1/). While waiting for the second injection (~0.2s) protons hop into the next buckets…

  9. Preventing Bucket Contamination: Coasting bucket Accelerated bucket

  10. Possible Scrubbing: • Construct a square pulse (occasional) monitor at extraction • Will do the job (scan through the interesting region), no danger to the calo detector. • Cheap • If we do find out that we need the extra extinction we can then build the external RFMM.

  11. 20TP in each filled bucket (FB) <40K Protons everywhere else (EB) E-O Measurement of Extinction at AGS • In AGS ring with two filled buckets • At extraction: 100MP in each filled bucket (FB) <0.1P in each empty bucket (EB)

  12. The electric field due to the beam at 1cm away, assuming the beam size < 1cm: • For filled buckets: Q=20TP, L100nsc=30m

  13. Analyzer QWP Laser E-O Crystal Photodiode, Amplifier Electro-optic Effect Pol. • The laser light acquires an ellipticity:

  14. Dielectric constant: e25 For 10-9extinction and 100ns1.3s: With 400,000 passes/AGS cycle in 0.5s:

  15. Proposal to use Fabry-Perot resonator with 1000 reflections, 1cm long (corresponding to 10m, less than the 30m of the beam base length): Protons Analyzer QWP Laser Photodiode, Amplifier E-O Crystal, Fabry-Perot resonator

  16. Dynamic range • Main signal: 35rad! (filled bucket) • Extinction: 35nrad (empty buckets), • i.e. dynamic range of 3107 • The best way to achieve the dynamic range is to use a light switch after the analyzer to gain three to four orders of magnitude.

  17. Using delta-rays with gas jet at AGS With a gas jet of 10-7 Torr equivalent we will get ~10 electrons With 10MeV energy per AGS cycle for 10-9 extinction. In 5 minutes there are ~30 electrons with 100MeV energy.

  18. Neutron Background: In g-2 (15m diameter ring) we injected 108 pions in a pulse of ~50ns, similar in number and time as our MECO proton pulses only 1.35s apart. The “near” calorimeters were gated back on 125s after injection! Electron energy threshold: 1GeV. The “far” calorimeters were gated back on 75s after injection! Neutron simulation needed for all extinction monitors.

  19. Comment on MECO note 138: • Arlene Zhang: They found no error on the calculations. • They claim the power requirement for the sinewave RFMM to be large… with cost implications. • I suggest we ask Arlene to give a presentation at the next MECO collaboration meeting at BNL.

  20. Summary • Extinction vs time between pulses • AGS mode of operation (1 vs 2 filled buckets-W.Glenn) • Two methods of measuring 10-9 extinction at AGS (E-O and delta rays) • Neutron background! • Limitations of the sinewave RFMM • Square wave sampling kicker-possibility of scrubbing • Need a presentation on MECO note 138

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