Status Update: Diamond Radiator Procurement and Processing for GlueX Richard Jones, University of...

GlueX collaboration meeting, Newport News, May 10-12, 2010

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Status Update: Diamond Radiator Procurement and Processing for GlueX

Richard Jones, University of Connecticut



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Outline• Thin diamond production

– laser ablation– chemical polishing– thin crystal cutting

• Mounting– carbon wires– smaller crystals


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Technique #1: laser ablation

Material is ablated (vaporized) from the diamond surface by a focused beam from a pulsed UV laser.

Each pulse creates a pit ~100 m diameter.

Rastering the beam over the surface of the diamond creates a smooth surface (sub-micron roughness).

Residual amorphous carbon on the surface is removed by chemical reaction (e.g. ozone, RIE process).


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152 µm 207 µm

Results presented by J. Smedley et.al.,BNL Instrumentation Group, Feb. 2009.

Deep ablation of polycrystaline sample:


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• Progress at UConn:– Pilot project funded ($13 K) by UConn Research

Foundation: Jan. 2010.– Laser installation, refurbishment, safety

procedures worked out: Jan. – June 2010.– Optics design and installation: May – Aug. 2010.– Design and installation of ablation chamber and

rastering stage: June – Sep. 2010.– First tests with diamond sample: Oct. 2010


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• Progress at UConn:– excimer gases highly corrosive,

tend to attack o-rings and seals.– all o-rings in the system have

been cleaned or replaced.– vacuum leak rate now 1 order

of magnitude below spec!– thyratron checks out, makes

sparks at the correct frequency– corrosive gas regulators, pump

filter, valves all in place, waiting for fluorine gas from vendor…


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• Progress at UConn:– first light pulses expected in ~1 week – then what?– UConn engineer/tech Brendan Pratt designed the optics setup (see below)


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laser beam fromexcimer (not shown)

laser pulsepower monitor

focusing lens (fused silica)

ablation plumeat an angle so the plumedoes not deposit on theablation chamber window

Optics setup, with vacuum chamberand CaF2 entrance window removed


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Technique #2: chemical polishing

Small Business Innovation Research (SBIR) grant proposal submitted to DOE in November, 2009.

Phase I – one year, feasibility studies, $100K total with $30K for UConn to carry out assessment with X-rays at CHESS

Notice of grant awarded: April 2010 !

Company: Sinmat Inc2153 SE Hawthorne Road, Suite 124 (Box 2)Gainesville Fl 32641-7553Phone / Fax : 352-334-7270

Principal Investigator: Arul ArjunanProject Title: Defect Free, Ultra-Rapid Thinning/Polishing

(20μm) of Diamond Crystal RadiatorTopic Number: 46 - Nuclear Physics Instrumentation,

Detection Systems and TechniquesSub-topic: e - Specialized Targets for Nuclear Physics Research


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Technique #2: chemical polishing

Goal will be to see if Sinmat can take a 200 micron diamond and thin it to 20 microns with their technique.

Challenges are:1. handling of 20 micron diamond – very fragile2. maintain uniform thickness3. keep original rocking curve width

Quality control process:1. obtain new monocrystals and characterize at CHESS2. pass at least one through the SINMAT process3. measure rocking curves again at CHESS


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Technique #3: thin layer cutting

• Method is potentially interesting for Gluex, but requires some new things:– access to IB facilities– new collaborators with this expertise– extrapolation of known process by

two orders of magnitude in thicknesstwo orders of magnitude in thickness

• Out of the blue from Element Six: mid-March, 2010– We have “some capabilities” for (laser?) cutting thin layers

from thick diamond substrates in one of our other facilities.– We just happen to have a We just happen to have a 10 micron thick10 micron thick sample of electronic sample of electronic

grade monocrystal 4.5 x 4.5 mm in area. Are you interested?grade monocrystal 4.5 x 4.5 mm in area. Are you interested?


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All Techniques: raw material

Element Six marketing: available for online orders

HPHT single-crystal plates:

HPHT synthetics

purity class: type Ib

500 microns x 4.5 mm x 4.5 mm

CVD single crystals:

CVD monocrystals

purity class: unstated

300 microns x 4.5 mm x 4.5 mm or 1.2 mm x 8 mm x 8 mm

167 £150 £ or 1800 £


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All Techniques: raw material

Element Six marketing: available by special order

Current belief in our group (based on limited data) HPHT monocrystals can have narrow rocking curves in places,

but need to carefully assessed and selectedcarefully assessed and selected. Electronic-grade CVD monocrystals have consistently narrow

rocking curves and have a much better growth morphology than HPHT samples we have seen.

narrow rocking curve crystals:

HPHT synthetics

purity class: type IIa

market: diffraction applications

electronic grade crystals:

CVD monocrystals

purity class: type III

market: electronic devices


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Procurement plans: raw material

Purchase the 10 micron diamond and assess to see if technique #3 can produce narrow rocking curve diamonds.

Purchase two each of the electronic grade and type IIa HPHT diamonds for work with SINMAT.

Purchase several of the non-electronic grade CVD monocrystals for testing the ablation process.


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Outline• Thin diamond production

– laser ablation– chemical polishing– thin crystal cutting

• Mounting– carbon wires– smaller crystals


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Mounting plans: carbon wires

Advantage of wires: minimize material in the tails of the electron beam, allow for full 90° rotation.

Advantage of carbon wires over tungsten: factor 5 times stronger per area factor 60 longer radiation length possibility to sinter carbon to the diamond

Disadvantages of carbon wires more brittle, can break when flexed cannot solder to the mounting frame

Samples and expert help obtained from Fermilab accelerator physicist with experience using carbon wires as targets.


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Summary Progress since January on all three

approaches to diamond thinning:

1. laser ablation – under construction

2. chemical polishing – project funded

3. thin crystal cutting – sample ordered

Mounting technique– carbon wires to replace tungsten– bench tests are underway

Status Update: Diamond Radiator Procurement and Processing for GlueX Richard Jones, University of...

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