corrosion of becu and vacuum setback in fermilab main injector · corrosion of becu and vacuum...

Corrosion of BeCu and Vacuum

Setback in Fermilab Main Injector

P. Hurh, A. Chen*, B. Brown, L. Cooley, J. Hylen, L. Valerio

The Fourth Workshop of Operation of LArge Vacuum systems,

Taiwan

April 1-4, 2014

Outline

• Fermilab MI and Upgrade

2013 at MI30

• Vacuum Setback

– Startup problems

– Huge gas load

– Corroded Copper seal

– Corroded BeCu spring

– Be contamination?

• Hunting for causes

– RGA scans

– Bi-metal galvanization?

– Radiation induced?

– Moisture?

– Be tests

• Summary

4/1-4/2014 A. Chen | Corrosion of BeCu and Vacuum Setback in Fermilab Main Injector 2


ANU Shutdown Details

Recycler Layout and Tasks

Key: WBS

Elements Removed

New Elements

Areas Affected

Stochastic Cooling Kickers

New Injection Area

Stochastic Cooling Pickups

Current Injection Area

Electron Cooling Insert

New Extraction Line

New RR30 Straight Current Extraction Area

New 53 MHz RF

MI 14 Building

(Off project)

MI 39 Building

(Off project)

New Abort Kickers

Proton

Direction

MI-308

By Cons Gattuso

Drawing of Pre/Post-ANU SD 309-308

309 308

307


Main Injetor/Recycler

Photo of Post ANU SD


Startup problems


• Cables mis-labeled

• IP/PS mis-matched

• Control card failure

• IP faulty- 1st evidence of corrosion

Corrosion on copper parts in 300 l/s ion pump just US of

308DS Collimator

Ion pump was shorted

Corrosion product on gasket appeared “pasty” and wet soon after removal

Some reports of funny smells

Ion pump had some “debris” and, when wiped with alcohol, showed some brownish residue

Original pump cleaned, new feedthrough and re-installed


Startup problems


• Huge Gas load ( IP in 15 min. protection mode)

• 308 area has larger IPs but Higher pressure

• High He background during leak-checking

Accelerator in Commissioning


• Commissioning degas a quite bit.

• Pressure in 308 still higher than normal startup

To meet schedule requirements, accelerator commissioning started despite high vacuum pressure


Time to investigate the huge gas load

Key: WBS

Elements Removed

New Elements

Areas Affected

Proton

Direction

MI-308

Lambertson Repalcement

Photo of Post ANU SD( event map)

Section 1

Section 1 Section 2 Section 3

Section 3

Section 3

Smoking

Cut

White

Residue

Heat test

Stained

Pump

Corroded

Pump

Corroded

Spring

Corroded

Pirani (originally on

bottom)

Most DS cut of

ANU mods


Corroded Al

seal

Corrosion(?) of 6”Aluminum seal at 308


308 elliptical bellows


308 bellows dissection


MI Elliptical Bellows (2.09”x4.84”)

BeCu172 spring


MI Elliptical Bellows

• BeCu spring used to keep RF fingers in good contact

• No corrosion found on the spares stored in shelf for

18+years

7.67g, Silver Coated


BeCu 172(Alloy 25) Beryllium: 1.80 - 2.00% Cobalt+Nickel+Iron: .6 max. % Lead: .02 max. % Copper: Balance

~1g of weight loss


Pirani Gauge Gasket

Note: Orientation of gauge was underneath the beam tube

in the original configuration, cross to 30 l/s Ion Pump.

On Beamtube

On Pirani gauge


White residue at DS of 308 Collimator • Partially “stuck” • Was found TiO

by SEM EDS result


“Smoking Cut” near BV309

• With Odor “diffusion pump oil with more of an exhaust or metal smell with it”

• Cutting was repeated on other similar tube, but no significant “smoking” observed, with odor of metal grinding


“Smoking Cut” near BV309, (Saw)


Swabs from the tube


• Black can be graphite from coating inside kickers

• “Oily” is dissolvable in acetone

RGA CART


RGA

• RGA scans taken before/after heating bellows

• Scan during the heating was not success since the pressure rise too fast (in seconds) to recorded before tripped

• Heating with “heat gun” too fast, more control is needed

64 is new

before

after 30 and 46 higher


CU/BE SPRING UNKNOWN CONTAMINATION

Image of samples in the SEM

EDS

4/1-4/2014 A. Chen | Corrosion of BeCu and Vacuum Setback in Fermilab Main Injector

25

Full field average of “Blue Powder”

• Did not pick up any Sulfur or Sodium or Potassium • Carbon could be from carbon tape used to mount powder specimen in SEM

chamber • SEM EDS analysis indicated: Cu, O, C, N • Note that EDS is unreliable for anything lower Z than 5 (including Be) • Donna noted that the powder was very “wet”, although that was not noted

when it was first observed (so very hygroscopic)

Name M. Mass color

CuO 79.5 black

Cu(OH)2 97.6 blue

CuCO3 123.6 Light blue

Cu(NO3)2 187.6 blue

Where were these from?


• Consistent with Copper

(II)Hydroxide (O:Cu = 2)

with some Copper

Oxide (O:Cu = 1)

• Measured 61/39 = 1.56

SEM EDS results of “Blue Powder”


Citranox (assisted) Bimetal galvanic Corrosion Test at NWA

• Test Objective

– Create corrosion through

galvanic potential (Cu gasket

to SS flange)

– Assisted by fluid film of 1%

Citranox (ultra-sonic cleaning

solution used on vacuum parts

in MI)

• Test Procedure

– SS chamber w/ cup of Citranox

sol’n with vent open to 70C

– Cooled to RT with vent closed

– Sit at RT for ? days

– Open and observe



• Heat Up

– About 3 hours to temperature

– No fluid loss visible

– Condensation on cooler window

• Cool Down Start

– Window cooled fast

– Lots of condensation on window

– Hard to get view of SS inner walls

– Used Heat gun (on cool) and observed color change

– Cu gasket on window flange not obviously wet



• After Cool Down

– Cooled to 18 C overnight

– Lots of condensation on

window

– Hard to see interior surfaces

• Heat gun on window

– Within seconds, window

cleared (except for very large

drop)

– Lots of condensation visible on

top 2/3 of chamber

– Lower third appears drier

– Some droplets on window

gasket?



• What to do next?

– Let sit for 1 week, open,

inspect?

– Heat top, Cool bottom?

• So far, no sign of corrosion on

Copper gasket in Window

Flange


More Corrosion Tests:

• 3 hydration corrosion tests – #7: Pure copper gasket sprayed with undiluted ammonia

– #8: Silver-coated copper gasket sprayed with undiluted ammonia

– #9: Silver-coated copper gasket dipped in 1% nitric

• All samples left to dry 24 October on watch glass

• Samples confirmed to be dry* 28 Oct. Watch glass

with samples then put into secondary container with

water and covered

Photographs taken 2 December

* “dry” may have been interpreted as a dry top surface

• Some corrosion is already evident

• Some moisture is visible where specimen and glass

touch, but the amount of moisture is smaller than that

observed on 2 December

6 November 2013 -

Tampa FL

30th Low Temperature - High Field Superconductor Workshop 32

Photo of #9 on 10/29/13

Hypothesis and Next Steps

• Dried nitric acid became re-activated with humidity

• 1% nitric residue corroded a large amount of material – Mass change will be measured

– Does the reaction terminate when all nitrate is consumed? If not, why not? Is it because nitrate catalyzes hydroxide formation?

• Liquid pooled either because: – Corrosion products are hygroscopic

– Some water was applied to the watch glass by mistake • We are repeating the experiment

• The liquid could be an effective electrolyte – We will measure pH and conductivity

– What happens if there is a SS counter-electrode?

• Residues have colors of expected salts – Black = silver nitrate, blue = copper nitrate or copper hydroxide

– We will perform EDS analyses

• But, 5% nitric spray on a silver coated small gasket was used in another test, but result varies.

6 November 2013 -

Tampa FL

30th Low Temperature - High Field Superconductor Workshop 33

Wet Chemistry Process?


Copper

CuO

Cu(OH)2

CuCO3

Cu(NO3)2

…

Nitric

(starter)

Silver

(catalytic

)

H2O

(wet)

silver nitrate provides an intermediate species to catalyze the formation of copper hydroxide via copper nitrate. That is, silver nitrate plus water provides nitric acid to attack copper and form copper nitrate, but then copper nitrate plus more water forms copper hydroxide and returns the nitrate back to the silver. Hence, the major reactant is water, the major product is the bluish copper hydroxide, and the catalysts are trace nitric acid and silver.

Air Ionization by Radiation

• During beam operation, primary protons in the residual gas of

the vacuum space and secondary particle flux in the tunnel

air ionize the air, creating some amount of nitric acid, ozone,

and other compounds.

– 0.2 gram of nitric might be possible with 1e-7 torr for 7 years of

operation

• To a much lesser extent, the same can occur from residual

(gamma) radiation.

– order of 1 milligram of Nitric compounds. With atmospheric

pressure and 10R/hr

• Neither process would seem to create enough acid in the

vacuum space to react with 1 gram of copper or more.


Moisture (permeation from roughing port)


O-Ring permeation

O2 H2O N2 total

rate 1.7 40 0.233

P psi 3.1 0.34 11.5

D inch 3 3 3

Q 1.3 1.3 1.3

s 0.2 0.2 0.2

L 1e-8 std cc/s 13.8 35.6 7.0 56.5

24% 63% 12%

after one

year std cc 4.4 11.2 2.2 17.8

mg 6.2 9.0 2.8

total rate std.cc/s 5.6E-07

torr.l/s 4.2E-07

Flood


Pumping Port is 9” from floor

Cons Gattuso

Beryllium Particulate

• It was realized on August 20, that the corrosion product from the BeCu spring (MI elliptical bellows) could have significant amounts of Be particulate. It was on the spring

• By the time ES&H was informed and the work was stopped (August 21), several more cuts into the system were performed.

• Work resumed under close supervision from ES&H with respirators (full-face or powered air purifying).

• Be test results indicated that a wipe sample of the blue corrosion product contained 350 micrograms of Be. Air samples of the 308 tunnel area and MI-60 drop area found no detectable Be.

• Currently any work on the MI vacuum system will be done under an HA which requires respirators and/or glove box and air sampling.

• Testing is currently underway to confirm this is a local phenomena associated with the 307-308 area

• Vigorous tests has been done for ES&H, No Be Contamination was found in other area or airborne


Summary

• The exact cause(s) of the corrosion remain unknown, many

hypothesis, but not confirmed.

• However, We believe Nitric component and moisture play critical

roles, as well as silver. silver nitrate provides an intermediate

species to catalyze the formation of copper hydroxide via copper

nitrate.

• Lessons learned: – Keep vacuum tube under vacuum, or completely sealed. Active

pumping shall implement for long shutdown

– Monitoring measure shall apply, as QA

– Keep open communication across groups to reduce risk of mis-

matching

• What we missed anything? Your suggestions are appreciated!


corrosion of becu and vacuum setback in fermilab main injector · corrosion of becu and vacuum...

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