Diamond Radiator Assessment Report on the CHESS run May 1-7, 2009 Richard Jones, Igor Senderovich, Franz Klein, Pawel Nadel-Turonski GlueX collaboration

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


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


The BNL diamond

It is pollenseason inConnecticut


The BNL diamond

• Optical image has “facets” that become visible when held at the right angle

• Surface or deep features?


The BNL diamond

• Crystal dimensions

4mm x 4mm x 300m


CHESS beamline C

Hutch

Diffractometer

CHESS staff member Ken Finkelstein


The GlueX monochromator

whitebeam

first crystalreflects upward

second crystalreflects back to horizontal



• Second mono crystal hangs upside down.

• Gravitational strain is “large”~ 400 nm



“ideal” monochromatedbeam shape

actual monochromatedbeam shape 2009

can displace backand forth by rockingthe mono angles

can take rocking curves


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



Interpretation of double-peak structureInterpretation of double-peak structure

t


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?



Hypothesis: maybe resonant, shift frequencyHypothesis: maybe resonant, shift frequency

add some large masses to the strings

shift down the frequencies byby ~ 1 order magnitude



343 343.2 343.4 343.6 343.8 344 344.20

0.2

0.4

0.6

0.8

1


Inte

nsity

FWHM800 r

factor ~4 worse!



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


Vibration-reduced mount

375.1 375.15 375.2 375.25 375.30

0.2

0.4

0.6

0.8

1


Inte

nsity

FWHM 10 r

consistent over entire

crystal !!

GlueX spec20 r RMS


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.


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!

Documents

Diamond Radiator Assessment Report on the CHESS run May 1-7, 2009 Richard Jones, Igor Senderovich, Franz Klein, Pawel Nadel-Turonski GlueX collaboration