diamond radiator assessment report on the chess run may 1-7, 2009 richard jones, igor senderovich,...
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Diamond Radiator Diamond Radiator Assessment Assessment
Diamond Radiator Diamond Radiator Assessment Assessment
Report on the CHESS run May 1-7, 2009Report on the CHESS run May 1-7, 2009
Richard Jones, Igor Senderovich,Franz Klein, Pawel Nadel-Turonski
GlueX collaboration meeting, Newport News, May 11-13, 2009
GlueX collaboration meeting, Newport News, May 11-13, 20092
Run Overview
• April 30 : install and align monochromator• May 1-4 : study monochromator alignment issues• May 4-6 : accelerator down, power short in
machine• May 6 : start scans of BNL diamond• May 7 : scans with BNL diamond remounted• May 8 : scans of Hall B diamond – radiation
damage assessment
GlueX collaboration meeting, Newport News, May 11-13, 20093
The BNL diamond
It is pollenseason inConnecticut
GlueX collaboration meeting, Newport News, May 11-13, 20094
The BNL diamond
• Optical image has “facets” that become visible when held at the right angle
• Surface or deep features?
GlueX collaboration meeting, Newport News, May 11-13, 20095
The BNL diamond
• Crystal dimensions
4mm x 4mm x 300m
GlueX collaboration meeting, Newport News, May 11-13, 20096
CHESS beamline C
Hutch
Diffractometer
CHESS staff member Ken Finkelstein
GlueX collaboration meeting, Newport News, May 11-13, 20097
The GlueX monochromator
whitebeam
first crystalreflects upward
second crystalreflects back to horizontal
GlueX collaboration meeting, Newport News, May 11-13, 20098
The GlueX monochromator
• Second mono crystal hangs upside down.
• Gravitational strain is “large”~ 400 nm
GlueX collaboration meeting, Newport News, May 11-13, 20099
The GlueX monochromator
“ideal” monochromatedbeam shape
actual monochromatedbeam shape 2009
can displace backand forth by rockingthe mono angles
can take rocking curves
GlueX collaboration meeting, Newport News, May 11-13, 200911
BNL diamond: first look
340 340.1 340.2 340.3 340.4 340.5 340.60
0.2
0.4
0.6
0.8
1
rocking angle (mrad)
Inte
nsity
FWHM200 r
GlueX spec20 r RMS
GlueX collaboration meeting, Newport News, May 11-13, 200912
BNL diamond: first look
Interpretation of double-peak structureInterpretation of double-peak structure
t
GlueX collaboration meeting, Newport News, May 11-13, 200913
Diamond mounting issue
Interpretation of double-peak structureInterpretation of double-peak structure
x
y
x = 200 Hzy = 180 Hz
Maybe a bad placefor mechanical vibrations?
GlueX collaboration meeting, Newport News, May 11-13, 200914
Diamond mounting issue
Hypothesis: maybe resonant, shift frequencyHypothesis: maybe resonant, shift frequency
add some large masses to the strings
shift down the frequencies byby ~ 1 order magnitude
GlueX collaboration meeting, Newport News, May 11-13, 200915
Diamond mounting issue
343 343.2 343.4 343.6 343.8 344 344.20
0.2
0.4
0.6
0.8
1
rocking angle (mrad)
Inte
nsity
FWHM800 r
factor ~4 worse!
GlueX collaboration meeting, Newport News, May 11-13, 200916
Diamond mounting issue
Radical approach:Radical approach:Get rid of the wiresGet rid of the wires1. remove diamond from
wire mount2. stick a clump of wax
on the end of a post3. stick the diamond into
the wax
GlueX collaboration meeting, Newport News, May 11-13, 200917
Vibration-reduced mount
375.1 375.15 375.2 375.25 375.30
0.2
0.4
0.6
0.8
1
rocking angle (mrad)
Inte
nsity
FWHM 10 r
consistent over entire
crystal !!
GlueX spec20 r RMS
GlueX collaboration meeting, Newport News, May 11-13, 200918
Also measured A full scan of the Hall B working diamond
( 50 micron “G50”) Was measured before in 11/2006 at CHESS –
first comparative measurementfirst comparative measurement! We think the radiation dose map since
11/2006 can be extracted from Hall B logs. First quantitative estimate of rad. damage.
GlueX collaboration meeting, Newport News, May 11-13, 200919
Status and Outlook Hopes that the new generation of CVD
diamonds from Element Six might be good enough for GlueX have been confirmed.
Existing monochromator crystals we have used at CHESS are not sufficiently rigid.
With new crystals, we can set up in a few hours and run a rocking curve in 30 min.
Wire mounting is problematic. New ideas are needed, or a more design with vibration damping.
Collaboration with BNL diamond Collaboration with BNL diamond development group promises to be very development group promises to be very fruitful for GlueX!fruitful for GlueX!