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

Large Angle Beamstrahlung
Radiation Monitor
Mikhail Dubrovin,
Ivan Avrutsky, Giovanni Bonvicini,
David Cinabro, Mike West
Wayne State University
July 14, 2003
ALC Workshop @ Cornell University, Ithaca,
NY
Outline
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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
Motivations for Large Angle
Beamstrahlung Monitor
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Physical motivations were discussed in numerous
publications and preprints, i.e. G. Bonvicini, J. Welch,
NIM 418, 223,1998; CBN 98-12, etc.
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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.
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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.
Degrees of freedom
at beam-beam scattering
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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
Expected BR signal
for beam-beam misplacements
The Program of Experimental
Study
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Stage 1: Radiation
Profile Monitor
Exp:Feb.2002Feb.2003
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Use it for alignment of
equipment
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Estimation of the rates
in VIS/NIR/IR spectrum
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Search for the signal
from beam-beam
scattering
Observe the expected
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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
Scheme of Radiation Profile
MonitorResults (see next
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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 beambeam scattering @ NIR
Radiation Profile Monitor @
CESR
Electro-mechanics
of the Radiation Profile Monitor
Stepping motor
Position sensitive
potentiometer
Moving slit
VIS PMT, E(beam)=1.8 GeV
VIS-PMT, E(beam)=3.7GeV
I+=5mA
I-=170mA
I+/I-=128/107mA
NIR-PMT with filter
E(beam)=4.2GeV @HEP
¼ of Beamstrahlung Radiation
Monitor
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PBS – Polarizing
Beam Splitter
(Glan-Laser, Calcite)
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BS – Beam Splitter
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M – Mirror
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HM – Hot Mirror
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IR/VIS PMT –
Hamamatsu Photomultipliers R316-02/
R6095
BR Detector at CESR
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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
Summary
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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.