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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
M. Sullivan
Machine Advisory Committee Review
December 13-15, 2004
IR NEG Heating and Upgrade
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Outline
• History from last run
• Summer work
• Vacuum model
• Conclusions
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
The NEG story
• When we regenerated the NEGs in IR2 on March 24 we began to wonder if some of the NEGs were starting to heat up from HOM power.
• MAC Review in April
• We confirmed that some were getting hot shortly thereafter but we did not get a full picture until the next ROD on June 3 when we instrumented every NEG in the upstream LER beam line.
Regeneration temperature is about 750 °F
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Upstream LER plan view
136Fside
160Fside
150Fbot
130Fbot150F
bot150Fbot
Collimators Quad chambersDipole chambers
268F
425F453F
724F
LER current 2.2 A
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Collimator
Collimator
724F
268F
453F
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Lab test data of NEG outgassing as a function of temperature
LER NEG Pump Temperatures
Upstream LER side
NEG Pressure vs NEG Temperature
0
1
10
100
1000
10000
0 100 200 300 400 500 600 700
NEG temperature deg F
NE
G p
ress
ure
(n
To
rr) 350 °F
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Data from the two hottest NEGs
NEG temperatures
Pump pressure of 3147. The ion pump is between the two NEGs
3142
3149
3149
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
LER NEG Test chamber
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Test NEG data over the summer
We held the test
NEG at our regen
temperature for a
month with a
Turbo pump
attached
Ave NEG pressure -- nTorr
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
6/27 7/2 7/7 7/12 7/17 7/22 7/27 8/1
Time
nT
orr
NEG temperature 725 °F
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Pressure in the test NEG
Pressure as a function of time in the test NEG.
Holding the NEG at the regen temperature of 725 F (400 C).
Ave nTorr
0
2000
4000
6000
8000
10000
12000
14000
16000
6/29/040:00
6/29/0412:00
6/30/040:00
6/30/0412:00
7/1/04 0:00 7/1/0412:00
Ave nTorr
-2000
0
2000
4000
6000
8000
10000
12000
14000
16000
6:00 7:12 8:24 9:36 10:48 12:00 13:12 14:24 15:36
After the first 6 hrs
After about 48 hrs
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Hydrogen Concentration Torr l/g
Hyd
roge
n E
quili
briu
m P
ress
ure
(Tor
r)
200°
C
300°
C
400°
C
600°
C
500°
C
St707
Em
britt
lem
ent
Lim
it (2
0 T
orr
l/g)
NEG heaters on NEG heaters off
Ion pumps off
Ion pumps on
•Heat NEGs for 1 hr•400-450 degC•Time 11:45-12:45•Tubro cart pump: 220 L/s •Pressure at pump about 10-5 Torr
Some regeneration details
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
LER upstream NEG work
• This summer:– We took out the nine NEGs with “c type” screens
and installed a small HOM absorber in each cavity– The total length of NEG pumping that was removed
is 5.5 m out of a total of 40.4 m– We removed the two movable collimators– We removed the Q4 NEG and have replaced it with
a HOM absorber (another 1.6 m of pumping)– We have added extra pumping at the port between
the upstream LER Q4 and Q5 chambers– In addition, we have added extra screening to the
ion pumps in this region
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Existing 3082 chamber
BPM
BPM
Chamber support
Cooling bar
NEG plenum
NEG heater
Quad extrusion
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Chamber showninverted and plenum not shown for clarity
SiC HOM absorber
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Part of one of the NEG pumps that was removed this last summer
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
One of the collimators that was removed
The NEG in this chamber was one of the hottest
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
HOM absorber to replace NEG pump
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Drawing of installed extra pumping
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Vacuum model
• We have started building a vacuum model of straight 2
• Had great help getting started by a summer student (Edward Young)
• We have a preliminary model of the LER upstream beam pipe
• Still need to check on screen conductances and on outgassing values from SR fans
• Nevertheless we can get some idea about what happens to the vacuum pressure profile with the above LER NEGs removed
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Chamber Model Layout
HER downstream
LER upstream
LER downstream
HER upstream
Support chamber
Q5 NEG
Q5 NEG
66.114 m
69.33 m
ST plot
plot
plot
plot
plot
12
3
4
5 6
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Support tube Vacuum Design Model
Vacuum pressure in the support tube.
The model predicts a pressure peak at the IP of about 20 nTorr.
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
No radial ion pumps
We lost these pumps a couple of years ago.
One developed an Argon instability before it died . Both pumps do not work right now.
We intend to replace these pumps during the next downtime.
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Upstream LER Ideal
LER beam line from Q2 septum to about 63 m upstream
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Upstream LER after summer down
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
HER scrubbing
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
HER Upstream Q5 chamber
• We plan to replace this chamber
BaBar Deadtime
Diamond BW (HER)
NEG temp in Q5 chamber
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
The upstream HER NEGs and heater instrumentation
The upstream HER beam pipe is also blanketed with NEG pumps starting at 21 m and going out to about 45 m from the IP
There are a total of 4 vacuum chambers in this region with NEG pumping (6 long NEGs). All of the pumps are below the beam chamber.
The screen is very similar if not identical to the “c type” screen seen in the LER
The collimator at 35 m has a TSP
The only chamber in this area without pumping is the fast kicker chamber
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
HER upstream NEG screen
This is a post at the center of the chamber
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
NEG heater temperature through heater resistance
• Stan Ecklund has installed a circuit that measures some of the heater rod resistances
• He has instrumented:
– LER upstream• Q4 + Q5 (same circuit)• BV1 + next outboard (3042) (same circuit)
– HER• Q5 downstream • Q5 upstream• BLF upstream
This particular NEG pump can not be instrumented any other way
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Temperature plot of first “c” chamber in LER (BV1)
Temperature plot of first “c” chamber in LER (BV1) using resistance measurement
Agreement is no better than about 20%. The signal is complicated by the resistance being the sum of the leads plus another NEG heater
BV1 NEG
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Q5 NEGsQ5
downstream
Q5 upstream
The upstream Q5 NEG resistance matches the TC we have in that NEG
Conclusion: Downstream HER Q5 NEG is hotter than the upstream HER Q5 NEG
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Upstream HER BLF NEG
This NEG is located 22-24.5 m from the IP
So far, this NEG looks OK
We think we will be OK for run 5
We have instrumented all of these upstream NEGs with TCs
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IR NEG heatingM. Sullivan
MAC ReviewDec. 13-15, 2004
Conclusions• We have fixed the NEG pumps in the upstream LER beam pipe that
were getting the hottest by removing the pumps and installing a HOM absorber in the pump cavity
• We removed the NEG pump that was closest to the septum chamber because HOM power was also heating up that pump and installed a HOM absorber in its place
• We removed the two movable collimators
• The run 5 beam parameters will increase the HOM power we have so far experienced by increasing the beam currents and shortening the bunches
• HOM power in IR2 will go up
• We have instrumented the upstream HER NEGs and we will be watching them very carefully during this coming run