large angle beamstrahlung radiation monitor mikhail dubrovin, ivan avrutsky, giovanni bonvicini,...
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Large Angle BeamstrahlungRadiation Monitor
Mikhail Dubrovin,Ivan Avrutsky, Giovanni Bonvicini,
David Cinabro, Mike WestWayne State University
July 14, 2003 ALC Workshop @ Cornell University, Ithaca, NY
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Outline● Basic principles of the large angle radiation monitor● First prototype of the detector for CESR and
results of the experiment● ¼ of the full scale prototype of the BR detector for
CESR-c and status of its installation● Summary
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Motivations for Large Angle Beamstrahlung Monitor
➢ Physical motivations were discussed in numerous publications and preprints, i.e. G. Bonvicini, J. Welch, NIM 418, 223,1998; CBN 98-12, etc.
➢ The idea is to exploit a large angle (comparing to ~1 beamstrahlung radiation from the beam-beam scattering at I.P. for monitoring of the beam quality parameters.
● In the short magnet approximation the radiation signal from the beam on beam scattering is expected in the IR range, 850-1200nm, 100% polarized (with factorized spec. & polar.)
● VIS or NIR ranges can be used for background subtraction.
➢ Notes on detector and optics design, simulation: CBN 98-12; CBN 98-26 PR E59, 4584, 1999; + conference presentations.
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Degrees of freedom at beam-beam scattering
● 7 d.o.f. Are important for luminosity tuning
● Radiating power, its spectral-angular distribution and polarization also depend on these d.o.f.
● We may measure the photon yield for two polarizations for both beams at twoangle
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Expected BR signalfor beam-beam misplacements
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The Program of Experimental Study● Stage 1: Radiation
Profile Monitor➢ Exp:Feb.2002-Feb.2003
➢ Use it for alignment of equipment
➢ Estimation of the rates in VIS/NIR/IR spectrum
➢ Search for the signal from beam-beam scattering
➢ Observe the expected profile of radiation
● Stage 2: ¼ of the full scale Beamstrahlung Monitor
➢ Exp:Aug.2003-June 2004
➢ Proof of principle optics, detector and experiment
➢ Alignment of equipment
➢ Study of the photon yield features for IR and VIS ranges and two polarization at fixed angular location
● Stage 3: Full scale BM @ 4 angular locations
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Scheme of Radiation Profile Monitor● Results (see next slides):
✔ Alignment
✔ Estimation of rates for radiation in VIS, NIR ranges (IR PMT requers T < -30C)
✔ We have observed an expected profile from SR
✔ First attempt to see the radiation from beam-beam scattering @ NIR range
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Radiation Profile Monitor @ CESR
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Electro-mechanics of the Radiation Profile Monitor
Moving slit
Stepping motor
Position sensitive potentiometer
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VIS PMT, E(beam)=1.8 GeV
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VIS-PMT, E(beam)=3.7GeV
I+=5mA
I-=170mA
I+/I-=128/107mA
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NIR-PMT with filter E(beam)=4.2GeV @HEP
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¼ of Beamstrahlung Radiation Monitor
● PBS – Polarizing Beam Splitter (Glan-Laser, Calcite)
● BS – Beam Splitter
● M – Mirror
● HM – Hot Mirror
● IR/VIS PMT – Hamamatsu Photo-multipliers R316-02/ R6095
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BR Detector at CESR● All parts and optics are in
hands
● IR/VIS PMT-s have been tested
● BR Detector will be installed at CESR by the end of July 2003
● Then we plan an alignment & physics shifts depending on status of CESR-c
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Summary● Beamstrahlung radiation looks very attractive for
beam quality monitoring.● Preliminary calculations shows the feasibility of
the large angle BR detector.● First prototype had been tested and shows an
expected profile of the background radiation from I.P. Region in VIS and NIR ranges.
● ¼ of full scale prototype is going to be installed @CESR in July 2003 for experiments with BR.