m.taborelli 2010/05/20

SPS MD run w17: e-cloud monitors and pressure rise

Coating news

By M.T.

m.taborelli 2010/05/20

q

51340 51480 51540

P 51824

StSt StSt

MBB dipoles

ECM

uncoated uncoated new a-C coated

m.taborelli 2010/05/20

1.00E-09

1.00E-08

1.00E-07

1.00E-06

1.00E-05

23:10:00 23:22:00 23:34:00 23:46:00 23:58:00

VGHB_51340

VGHB_51480

VGHB_51540

VGHB_51824

1x72 bunches 450 GeV

less than 5E-9

Static pressure and start of MD, unstable beam, large losses

Highest pressure in freshly inserted ECM StSt

Highest pressure in freshly inserted uncoated dipole

lowest pressure in old conditioned uncoated inserted dipole27.04

P[m

bar

]

-Static pressure as usual (for instance w25/09 or w45/09)

q

51340 51480 51540

m.taborelli 2010/05/20

1.0E-08

1.0E-07

1.0E-06

1.0E-05

00:00:00 00:30:00 01:00:00 01:30:00 02:00:00 02:30:00 03:00:00

p [m

bar]

uncoated refcoateduncoated newECMdrift space after ECM

nominal int. 4x72 bunches accelerated

Second night of MD, stable beam, very low losses

29.04.101.0E-08

1.0E-07

1.0E-06

1.0E-05

29.04.2010 01:26:24

p [m

bar]

uncoated refcoateduncoated newECMdrift space after ECM

nominal int. 4x72 bunches accelerated

-Conditioning is very weak-Difference in dynamic pressure due to history more than coating-large pressure rise in ECM (as before)

m.taborelli 2010/05/20

StSt.

-Almost no conditioning of StSt; one monitor with 2 times more signal than the other-Decrease in current in carbon monitors …due to (weak) pressure decrease?

Uni

t: in

tegr

ated

ele

ctro

n cu

rren

t ove

r sup

ercy

cle

(nC)

inte

grat

ed F

BCT

over

sup

ercy

cle

(1e1

0pro

tons

/bun

ch) E-cloud monitors

a-CNe13a-CZr

x104

m.taborelli 2010/05/20

Pressure rise comparison: data of MD w25/09

1.00E-08

1.00E-07

1.00E-06

12:00:00 00:00:00 12:00:00 00:00:00 12:00:00 00:00:00

time

pre

ssu

re m

axx

51480

51540

51340

15/6 16/6

48 bunches 2 - 3 batchesno accel

72 bunchesno accel1 batch

change of tune

72 bunchesno accel2 batches

17/6

72 bunchesno accel3 batches

72 bunches with acceleration

3 batches

4 batches

2010 w17 2009 w25

4b3b

- No significant differences except for the higher pressure in the recently inserted dipole51480

m.taborelli 2010/05/20

Fast pressure acquisition (300Hz)

4 batches with acceleration

P[m

bar]

Synchronization with FBCT clearly shows the effect of each batchThe minimum of pressure is at second injection

The differences in individual shapes are not understood

Inte

nsity

10

10p

/b

m.taborelli 2010/05/20

Comparison fast and normal (PVSS, 1s) acquisition

Synchronization accuracy 1s due to PVSS (1s resolution)

Still some calibration to be corrected on data of 51480

m.taborelli 2010/05/20

Next liners after w22

StSt grooves insert, (M.Pivi)Inserts just arrived at CERN

Partial a-C coating to verify the effect of e-cloud close to a-C: -non uniform in lateral direction to profit of resolution of strip detector

2 half shells

m.taborelli 2010/05/20

Coatings

-half-length chamber with MBB profile coated (SEM for thickness profile in progress): more uniform with rectangular cathodes than cylindrical excepted for the gap between rods (see figure).

-7m prototype next week; then 7 m real MBB chamber (with rectangular cathodes)

-Coated 2 liners for ECM in the SPS: SEY=0.95 after one week air exposure! (high power => high deposition rate and high resulting substrate temperature ~250C)

-Coated tube for ion induced desorption experiment in Linac 3 (running)

-Characterization: pumpdown measurements done on CNe53 (round tube) confirm 10x higher outgassing of a-C wrto unbaked StSt

-Asked two firms for a sample with alumina plasma spray to test first degassing and dielectric strength

m.taborelli 2010/05/20

Coating with rectangular cathodes

Defects of the substrate

“plasma rings” at extremities

Defects due to a gap in the cathode(new cathode design tested today)

m.taborelli 2010/05/20

Next on SPS :-w22: replace the ECM and intermediate section with a-C coated ECM and measure again the dynamic pressure simultaneously with e-cloud

-w22: remove dosimeters (measurements of dose to identify possible location of RGA electronics to identify desorbed gases)

-w26: extract removable sample for SEY analysis (to verify the effect of e-bombardment on the a-C coating)

-w30: insertion of coated MBB (3 m prototype OK, tubes ready for end of May probably with rectangular cathodes)

-w26 or w30: replacement of a-CZr ECM with half-coated ECM

-at the next venting of dipoles we could isolate a pumping port (pressure gauge+ion pump) through a manual valve from the main vacuum system of the machine to verify the behavior with beam and magnet ramp

m.taborelli 2010/05/20

m.taborelli 2010/05/20

1.00E-08

1.00E-07

1.00E-06

1.00E-0500:02:53 00:03:14 00:03:36 00:03:58 00:04:19 00:04:41 00:05:02 00:05:24 00:05:46 00:06:07 00:06:29 00:06:50 00:07:12 00:07:34 00:07:55 00:08:17 00:08:38

VGHB_51340

VGHB_51480

VGHB_51540

VGHB_51824

VGHB_51877

Effect of the magnets on the gauge signals