The Advanced Photon Source is an Office of Science User Facility operated for the U.S. Department of Energy Office of Science by Argonne National Laboratory

APS PC Gun Laser Repair J. Dooling

June 10, 2015

J. Dooling PC Gun Drive Laser Update—Repair PIP Meeting June 10, 2015 page 2 / 18

Synopsis

Last time we met (PiP May 13th), recently discovered a green-blue material covering the surface of the rods

Had just completed measurement of pump laser diodes at Fermilab—slope efficiency of existing set was found to be 17% lower than spare set.

Since our last meeting, tried re-aligning the regen with existing rods and diodes in order to optimize Pockels Cell (PC) voltages and minimize multipulse output

Measured PC voltages (DC and AC) and found they were low—S. Edstrom (SLAC) said he could send us a new PC HV power supply

Could not get cavity to lase Clean rods in place vs. pull heads apart to take samples of the surface material Offered NALCO cleaning solution 460-2567 by A. DiChiara May 15th, sent photo of surface material to Schott (rod manufacturer) Initial comment from Schott engineer (May 15th) was material could be algae—

phosphate in glass acts as a slow-release fertilizer. Engineer would pass photo on to Schott technical staff

Did not hear back from Schott until May 27th

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Comparing PC Voltages from 2013 and 2015

S. Edstrom (5/20): “The static DC voltage to the HSD's should be ~5 kV. The actual HV pulses measured at the cells should be ~4.2 kV...you seem far below that.”

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Synopsis, con’t In the mean time, had chiller water tested by the Analytical Chemistry Lab (ACL) in

Bldg. 205, contact: Sr. Chemist Don Graczyk Brought water samples to ACL May 20—test results returned May 22 pH: 4.76±0.10 “Copper and zinc are present at substantial concentrations (2 and 3 mg per lt or 2

and 3 ppm) and suggest attack on brass (Cu/Zn alloy).”—D. Graczyk Graczyk suggested material could be copper carbonate: color is correct and is

water insoluble PC HV PS from SLAC arrived May 28; tested with DEEI A. Brill June 2 May 29, Schott Research Fellow Joseph Hayden requested a sample of the surface

material. Also in response to query regarding use of cleaning solution he said, “We also feel that NALCO 460-CCL2567 cleaning solution may be to [sic] aggressive for LG-760.”

Formulated plan to disassemble heads, extract surface material, and exchange rods—discussed with J. Power June 2. Disassembly follows 2013 procedure.

Removed heads from regen, cleaned remainder of chiller system with 50:50 NALCO 460-CCL2567 and distilled water (R. Wright)—flushed with distilled water June 4th.

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Synopsis, con’t

Now running OptiShield corrosion inhibitor 10:1 solution (1 part OptiShield, 9 parts distilled water).

Monitor pH—should start at 10.4 (slightly basic); if it drops below 9 replace No UV, but can still use turbidity meter Collected material from rod using dental pick (relatively soft plastic) onto

microscope slide June 3rd Tests conducted at ACL using Energy Dispersive Spectroscopy with Scanning

Electron Microscopy (EDS/SEM) June 5th Confirmed the presence of copper, carbon, and zinc Cleaned first rod with nitric acid later in the day June 5th Collected sample for Schott from second rod June 6th and cleaned second rod;

fracturing noted Graczyk suggest cleaning 2013 rods with nitric acid might also be useful—did this

June 9th Shipped surface material from second rod to Schott June 9th

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“Basic” copper carbonate

if surface contamination is basic copper carbonate, then material can be removed with an acid solution

D. Graczyk suggested a weak nitric acid:

copper then goes into solution

Cu2(OH )

2CO

3+H +NO

3

→ (H 2CO

3⇔CO

2+H

2O)+Cu

+++2 NO3

rod from DS head

rod cleaned in 2013 (alumina)

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EDS/SEM testing at ACL in Bldg 205

sample from first rod—on microscope slide

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SEM imagecarbon tape lifts off material from slide and provides a conductive base

—preliminary results from ACL report, D. Graczyk and S. Lopykinski

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Element Weight% Atomic%

C K 6.41 12.79

O K 44.56 66.81

P K 6.40 4.95

Cu K 38.66 14.60

Zn K 1.51 0.55

As L 0.00 0.00

Pt M 0.92 0.11

Pb M 1.55 0.18

Totals 100.00

Element Weight% Atomic%

C K 17.02 28.26

O K 39.41 49.12

Mg K 0.47 0.38

Al K 0.33 0.24

Si K 19.35 13.74

P K 3.93 2.53

K K 0.17 0.09

Cu K 14.95 4.69

Zn K 2.38 0.73

W M 1.99 0.22

Totals 100.00

high copper, no silicon (3 of 6) high copper, high silicon (3 of 6)

EDS/SEM analysis, con’t—two types of material found

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EDS/SEM analysis, con’t—two types of material found

high copper, no silicon (3 of 6 spectra) high copper, high silicon (3 of 6 spectra)

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Cleaning with weak nitric acid solution

before cleaning after cleaning

relatively thick deposits etching is visible

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During and after cleaning, illumination from the side reveals defects or fracturing

during cleaning after cleaning

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PC Gun Laser system work

I. Flush & ready Chiller/Water SystemA) remove heads and reconnect coolant lines

B) clean chiller and lines with Nalco 460-CCL2567 cleaning solution

C) flush with distilled water, repeat

D) refill with 1:10 optishield to distilled water and monitor pH

II. Rod ExchangeA) take heads to lab (L3119) and disassemble

(use 2013 procedure)

B) collect samples of surface material from rods (using plastic DenTek Deep Clean Dental Picks to remove material from surfaces of rods)

C) deliver surface material sample to Chemistry for analysis (D. Graczyk, x3489, Bldg. 205)

D) reassemble heads using rods removed in 2013 (use procedure rodReplacementProcedureJMAR)

III. Head install & alignment on lab table (includes final diode check with ohm-meter, checking connecting straps, and bolts tight)

A) align rods, transmission

B) align rods, reflection

C) replace pump laser diodes with spare diodes (follow procedure pumpDiodeReplacementProc)

D) verify rod alignment

IV. Clean existing laser rodsA) collect 0.015 molar nitric acid solution

from D. Graczyk

B) clean heads with ethanol, inspect o-rings and water surfaces

C) clean rods with nitric acid, rinse with distilled water, dry with ethanol (acetone); inspect barrel surfaces

V. Replace PC HV Power Supply (inspect and test)

VI. Reassemble heads and return to the regen in LR and begin alignment

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Summary

Don’t run laser chiller without corrosion inhibitor Monitor pH—must keep above 9. Will monitor weekly. Flush coolant regularly—every run Present set of rods might be useful as spares but show damage 2013 rods appear in better shape and will install these Pursuing quote for new rods Will begin reassembly of heads after new o-rings arrive this week Can probably continue to use existing pump diodes Will install new PC HV PS Will use beam purity monitor—have new EOT2030 detector (IR, Vis, or UV)

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Additional slides

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Replaced flashlamp- with diode-driven heads in 2010

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Diode-driven heads

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Regen output—possible location for beam purity monitor