diamond radiator development richard jones gluex collaboration meeting, newport news, jan. 28-30,...

Diamond Radiator DevelopmentRichard Jones

Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010

Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 2

Outline

• Producing thin crystals– three promising techniques– SBIR grant proposal (technique #2)– excimer laser project (technique #3)– risks, timeline, decisions

• Mounting thin crystals– two challenges– observations at CHESS – observations on the bench at UConn– ideas for mitigation– risks, timeline, decisions


Three promising techniques

1. Ion implantation, chemical etching, and lift-off

2. Chemically-assisted mechanical polishing

3. Laser ablation and reactive ion etching


Technique #1: ion implantationMethod in use by groups in UK and Japan, perhaps elsewhere

step 1: set ion beam energy for a specific depth, sweep over area of the crystal

high-quality thick diamond monocrystal

step 2: heat the crystal. The thin deposition layer converts to graphite.

heating anneals the crystal, creates graphite layer

step 3: laser-drill trenches around the edges and inject solution to etch the graphite chemical etch dissolves graphite, but not diamond



step 4: braze a tiny wire to the thin crystal and simply lift it off the substrate



step 4: braze a tiny wire to the thin crystal and simply lift it off the substrate

Very thin crystals (400 nm) have been made with this technique.

Possibly the only way to make diamond monocrystals thinner than 1m.Many thin crystals can be cut from a single thick substrate.

Discussion with experts: Never considered anything as thick as 20m!Ion bombardment energy must be increased,so would need a specialized ion beam facility.


Technique #1: ion implantation

• Method is potentially interesting for Gluex, but

– requires new collaborators with expertise in ion beam techniques (University of Strathclyde, Glasgow???)

– requires access to IB facilities (may be available at Jlab in accelerator group for cleaning RF cavities???),

– requires extrapolation of known process by 2 orders of magnitude in thickness (range is easy to calculate, but will increased energies damage the pristine crystal in new ways?)


Technique #2: chemical polishing• Improves on mechanical polishing alone by reducing the

forces needed to achieve a given material removal rate.• Mechanical abrasion techniques are know to work, but

they all suffer limitations:

a) low removal rates

b) poor surface finish

c) extensive sub-surface damage

d) poor scalability in manufacturing.


Technique #2: chemical polishing

Basic idea of process:1. Chemicals coating slurry particles

undergo pressure-catalyzed reaction with diamond surface.

2. Mechanical abrasion removes the softened surface material.

Diamond + chemistry + coated particle soft surface layer [–C–C] [–C–O]

Diamond soft layer + coated particle removal of soft surface layer, leaving clean diamond surface [–C–O] [–C–C]

process under development bySinmat Inc., Gainesville, FL


Technique #2: chemical polishing• Small Business Innovation Research (SBIR) grant proposal

submitted to DOE in November, 2009.

• Phase I – one year, feasibility studies• Budget – $100K for phase I, $30K for UConn• Currently under review at DOE

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


Technique #3: laser ablation1. Material is ablated (vaporized) from the diamond

surface by a focused beam from a pulsed UV laser.

2. Each pulse creates a pit ~100m diameter.

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

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

• Technique being perfected by the BNL Instrumentation Group• Results from BNL described at previous Gluex meetings• Agreement (informal) with BNL group to cooperate with Gluex

– Gluex needs its own laser ablation capabilities

– BNL will compare results, advice, help with surface characterization


Technique #3: laser ablation

• As of the last collaboration meeting 9/2009:– Excimer laser with sufficient power, pulse rate found at UConn.– UConn laser last used 1998, needs refurbishment.– JSA proposal for $15,000 to refurbish laser was declined.

• News as of 12/2009– Proposal submitted for internal funding at UConn under the

Large Faculty Grant competition in Oct. 2009.– $13,000 requested for materials, supplies, student labor.– $5,000 additional in NSF grant operating funds to be devoted to

project for student labor.– Request approved for full amount for period Jan.-Dec., 2010.


Laser refurbishment plan• First, take the proper safety course required by the University of

Connecticut Environmental Health and Safety department.

• Prepare Dr. Well's laboratory for the transfer of the excimer laser including setup of ventilation, three-phase (208V) power supply, cold water distribution and collection, and a sturdy table to put the laser on.

• Replacement of halogen filters

• Tend to the vacuum system: replace oil in diffusion pump, test for serious leaks at moderately low pressure (10−6 Torr)

• Test the RF generator (most expensive/hard to replace!)

• Procure a bottle of pure Ar gas

• Check internal circulating fan bearings, as these are a possibly source of corrosion

• Flush the tube, turn it on and test output power


Laser refurbishment: current status

• Gas lines have been installed with new Swagelok fittings.

• Gas solenoids have been repaired and the system has been charged with fresh Helium to 2600mbar.

• Currently the system is leaking >25mbar per hour and we plan on replacing o-rings in main laser window to fix this.

• Optics will be cleaned once we receive our new supplies and the laser must be realigned using a HeNe laser.

• A Veeco Helium Leak Detector was used to check for leak sites. The front window has the largest source of Helium at the moment and the o-ring will be replaced shortly. Also, a number of the "spark plugs" that discharge into the laser had noticeable leak rates and I hope to service them shortly.


Laser refurbishment: progressing well

Project specialist (and group brewmaster) is UConn grad Brendan PrattBrendan Pratt(see http://zeus.phys.uconn.edu/wiki/ for updates)

http://zeus.phys.uconn.edu/wiki/


Risks with our approach• Two complementary techniques

– laser ablation is the standard option– RCMP is the backup option (depends on SBIR funding)– RCMP may be useful with laser ablation (clean ablated surface)

• A lot depends on what happens in the next 12 monthsthe next 12 months:– Laser refurb. does not hit a show-stopper – none in sight– Sinmat’s interest in our project is maintained

• depends on SBIR funding• or finding another source of funds

– Our collaboration with CHESS staff is maintained• we should carry out the upgrade they requested

– We can procure a set of Element Six diamonds of our own


Mounting thin diamond crystals

Two challenges:1. mechanical vibration

2. stability of adhesive at elevated temperatures


Mounting thin diamond crystalsObservation of vibration at CHESSObservation of vibration at CHESS

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

Inte

ns

ity

(a

rb.

un

its

)

200 r (actual)

8 r (expected)

343 343.2 343.4 343.6 343.8 344 344.20

0.2

0.4

0.6

0.8

1


Inte

nsity

375.1 375.15 375.2 375.25 375.30

0.2

0.4

0.6

0.8

1


Inte

nsity

Inte

nsi

ty (

arb

. u

nits

)

10 r FWHM


Undergraduate student Chris Pelletieraligns the Michelson Interferometerthat he built.

diamondcrystal

mountingwires

Mounting thin diamond crystalsObservations on the bench at UConn


Video of “Flare” Spot MotionImages taken with a high-speed camera: 1200 frames/s.Direct laser spot does not move, but creates a “flare” spot that we calibrated to the rotation angle of the wafer.

windows video

quicktime video

http://zeus.phys.uconn.edu/halld/glueXmeetings/mtg-1-2010/michelson_movie.avi

http://zeus.phys.uconn.edu/halld/glueXmeetings/mtg-1-2010/michelson_movie.mov

http://zeus.phys.uconn.edu/halld/glueXmeetings/mtg-1-2010/michelson_movie.mov


Flair Spot v. Time (Images)

T=0s T=.000833s

T=.001667s

T=.0025s T=.004167s T=.005s

T=.005833s

T=.00667s T=.0075s


DFT of time-domain signals

• A single dominant resonance ~18 Hz is visible in both x and y.

• A fun undergraduate research project: tune the fundamental resonance frequency and measure the power spectrum of the driving force.

• Solution: push fundamental resonance up to where F() is weak.

Horizontal Motion Vertical Motion


Mounting thin diamond crystalsChallenge #2: operating temperature

tem

pera

ture

(K

)

x position (cm)

y position (cm)

Operating temperature for20m diamond for highintensity GlueX running.

New resultNew result: now includes conduction through 18m diameter W wires.

Temperature is ~420° C, down from 520° C with radiation alone,

but still too high for epoxy.


Mounting thin diamond crystalsChallenge #2: high-temperature adhesives1. ceramics – epoxy vendor recommendation

2. brazing – diamond experts say this works best

3. use a pinch-mount – avoid adhesives altogether• requires more mass near the beam• might grip in one corner• esp. interesting if diamond thinning allows for fat edges

grip the corner


Risks with our approach

Vibration must be reduced 2 orders of magnitude• wires are now anomalously long, can be reduced by factor 5

• can go from tungsten to carbon fiber, more strength/Z2

• response dominated by match between resonances and power spectrum of building vibrations – should drop rapidly with frequency

• bench tests have resolution to just detect diamond motion down to 10r p-p so we can optimize the mount using our interferometer.

• a solution that meets our requirements is yet to be demonstrated

Epoxy mount (e.g. Mainz, Hall B) may fail in Hall D• several workable solutions exist• which one is best depends on the final morphology of the diamond


Timeline and decisions: 2010Mar. 1, 2010: Funding found to buy diamonds from Element

Six, and submit order for 3 samples.

May 1, 2010: If diamonds are available, measure at CHESS, otherwise next window is Nov., 2010.

June 1, 2010: UConn laser is working, or we need another solution.

July 1, 2010: Sinmat’s SBIR was approved, or we need to find another funding source to work with them.

… if all above milestones were met successfully, then

Oct. 1, 2010: Obtain first thinned diamond back from Sinmat

Nov. 1, 2010: Mount Sinmat diamond, characterize at CHESS.


Summary and outlook

• A number of open issues remain to be answered before we can procure radiator diamonds for GlueX.

• Diamond radiator development is the top priority for the UConn group in 2010.

• Detailed work plan set out for the period up until mid-summer with milestones and decisions.

• Purchase of diamonds from Element Six is now on the critical path for this development.


Questions

diamond radiator development richard jones gluex collaboration meeting, newport news, jan. 28-30,...

Documents

newport news

ion implantation method

substrate slide

reactive ion

decisions slide

ion beam energy

ion bombardment energy

diamond surface