Large Angle Beamstrahlung Radiation Monitor

1. Mikhail Dubrovin, Ivan Avrutsky, Giovanni Bonvicini, David Cinabro, Mike West Wayne State University July 14, 2003 ALC Workshop @ Cornell University, Ithaca, NY Large Angle BeamstrahlungRadiation Monitor

2. 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

3. 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/g) 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.

4. 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 two fangle

5. Expected BR signalfor beam-beam misplacements

6. 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 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

7. 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

8. Radiation Profile Monitor @ CESR

9. Electro-mechanics of the Radiation Profile Monitor Stepping motor Position sensitive potentiometer Moving slit

10. VIS PMT, E(beam)=1.8 GeV

11. VIS-PMT, E(beam)=3.7GeV I+=5mA I-=170mA I+/I-=128/107mA

12. NIR-PMT with filter E(beam)=4.2GeV @HEP

13. 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

14. 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

15. 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.