M.J. Barnes 1

MKI Operational Experience and Future Plans

M.J. BarnesAcknowledgements: L. Ducimetiere,

N. Garrel, B. Goddard, J. Uythoven, ….

LIBD: May 17, 2011

M.J. Barnes 2

Overview of injection region (IR8)

Ceramic Capacitor

LIBD: May 17, 2011

MSI

TDI

4 MKImagnets

Ecloud solenoids

• 4 transmission-line kicker magnets per injection system• Total of 0.85 mrad (Vertical)• 2.65 m length per magnet• 0.9/3.0 µs rise/fall time• Ceramic vacuum chamber with conducting stripes –

various generations of shielding presently installed.

Magnet in the vacuum tank with ceramic beam pipe

Ferrite

M.J. Barnes 3

MKI’s: Strong Sparks (Electrical Breakdown) During Pulsing of Kicker System

July 12, 2010: MKI8 magnet D, strong spark during SoftStart @ 53.3kV and 6µs; July 14, 2010: MKI8 magnet D, strong spark during SoftStart @ 53.3kV and 2µs.

August 21, 2010: MKI2 magnet B, strong spark during injection (TMR current pulse ~1/2 duration); September 27, 2010: MKI2 magnet B, strong spark during injection (TMR current pulse ~1/2 duration);

October 16, 2010: MKI8 magnet D, strong spark during injection; October 27, 2010 @17:56: MKI2 magnet B, strong spark during injection; April 18, 2011 @ 00:06: MKI8 magnet D, strong spark during injection (double current in MS).

LIBD: May 17, 2011

NOTES:POINT 2 (Clockwise Inj.) 49.6kV (7.8µs) nominal for injection, 52.6kV during SoftStart: MKI2 magnet B changed during Christmas Technical Stop 2010-2011.POINT 8 (Anti-Clockwise Inj.) 51.3kV (7.8µs) nominal for injection, 54.3kV during SoftStart.

M.J. Barnes 4

MKI8: MS, PFN D, Current

LIBD: May 17, 2011

Electrical breakdown in MKI8-D on April 18, 2011 (double current in MS)

From Christmas Technical Stop 2010-2011, we have the ability to log and view MS current with TIMBER.

M.J. Barnes 5

E-cloud Solenoids

Depending upon the sources of electron cloud (to be identified during 2011 operation), Ecloud solenoids may be required to be installed between MKI’s.

Electron Cloud solenoids are presently installed close to Q4 & Q5 (slide 2). The solenoids have been turned-on as from 18 April 2011 @ 17:37hrs. However to date there has not been a “controlled” experiment to determine their effectiveness.

LIBD: May 17, 2011

M.J. Barnes 6

Vacuum Activity During Scrubbing

Notes: Pressure with 50ns spacing: ~1.3e-8mbar on magnet D, <8e13 beam intensity, 450GeV – see next slide for zoom.

LIBD: May 17, 2011

Number of bunches for circulating beam include: Sat Apr 9th (50ns): 07:00hrs 12 + 4x72 circulating 10:24hrs 588 for both B1 & B2.

Sun Apr 10th (75ns): 11:44hrs 804 B1, 732 B2 17:27hrs 444 for both B1 & B2 17:46hrs 732 for both B1 & B2 18:05hrs 804 for both B1 & B2

23:51hrs 300 for both B1 & B2 Mon Apr 11th: 00:20hrs 804 B1, 732 B2 00:33hrs 804 for both B1 & B2 00:51hrs 876 for both B1 & B2 01:01hrs 948 for both B1 & B2 01:13hrs 1020 B1, 948 B2 01:19hrs 1020 for both B1 & B2

Jumps in vacuum pressure (magnet D) not yet understood.

50ns

Note: Ecloud coils close to Q4 & Q5 0A (off before 18 April 2011)

M.J. Barnes 7

Vacuum Activity During Scrubbing - 50ns beam

Note: Ecloud coils close to Q4 & Q5 5ABeam intensity < 8e13. 450GeV. Pressure rise in an MKI tank occurs during injection.

LIBD: May 17, 2011

Note: Ecloud coils close to Q4 & Q5 0A (off before 17:37hrs on 18 April 2011)

8

Vacuum Activity During Normal Operation

From above: maximum pressure measured in an MKI tank is generally 1.5e-9mbar and occurs during injection. An exception is pressure in MKI8-C at ~05:10hrs on 02-05-2011 (~3e-9mbar) – see slides 10 & 11.

Note: Ecloud coils close to Q4 & Q5 5A (from 17:37hrs on 18 April 2011)

LIBD: May 17, 2011 M.J. Barnes

M.J. Barnes 9

BLM Layout at Points 8 & 2

LIBD: May 17, 2011

P8

23469

MKI.D5R8.B2MKI.C5R8.B2

BLMEI.05R8.B2E10_MKI.D5R8.B2

BLMEI.05R8.B2E20_MKI.C5R8.B2

DCBA

P2

Injection

D C B A

Slide courtesy of Barbara & Slava

P8: BLM name corrected as from TS of May 2011

10

Beam Losses at Injection: 02-05-2011

During the above pressure (slow) rise there does not seem to be a correlation of vacuum with: beam loss, cryogenics temperature (see next slide) or bunch length.In above case, highest pressure was measured in interconnect between magnets C & D, suggesting the interconnect or the ceramic beam-pipe in C & D may be the origin of the rise.

LIBD: May 17, 2011 M.J. Barnes

Bunch length

MKI-C5R8Energy

MKI-D5R8

Intensity

Note: Ecloud coils close to Q4 & Q5 5A (from 17:37hrs on 18 April 2011)

11

Beam Losses at Injection: 02-05-2011

During the above pressure (slow) rise the highest pressure is measured on the B2 Penning gauge, on the interconnect between magnets C & D, suggesting that the interconnect or the ceramic beam-pipe in magnets C & D may be the origin of the rise: little pressure rise is measured between magnet D and Q5. Hence, in this case, there is no correlation with the Q5 cryogenics.

LIBD: May 17, 2011 M.J. Barnes

DCB

BEAM 2

M.J. Barnes 12LIBD: May 17, 2011

Longitudinal Beam Coupling Impedances of several MKI’s have been measured, together with several different beam screen configurations. Power deposition is calculated from the real beam coupling impedance and the spectrum of the beam, assuming a cos2 bunch profile at top energy (7 TeV), which is a pessimistic assumption. Power deposition of 2400W/m if no screen installed !!; One installed MKI has 24 screen conductors (9 short), the others have 15 installed; 6 installed MKI’s have 2 damping resistors (in parallel with ferrite tube), the other 2 MKI’s (MKI8-C & MKI8-C) have only 1 damping resistor installed; Measurements exist for 5 of the 8 installed MKI’s; Calculated power depositions, for 5 of the 8 installed MKI’s, range from 60W/m (MKI2-A) to 97W/m (MKI2-B).

Beam Induced Heating of Ferrite

M.J. Barnes 13

Ferrite Heating: Measurements in Clean Room

PT100 on ground plate of magnet

PT100 on ferrite of “tube”

Ceramic tube

PT100 setup for installed MKI’s

Note: both PT100’s installed for measurement of magnet temperature, in clean room, gave same reading to within ± 4 ˚C.

Conclusion: for measurements in clean room, Curie point of ferrite corresponded to 106 ˚C measured on ground plates (dissipation of 172W/m in “heater element”).SIS interlock presently 55 ˚C (see next slides).

LIBD: May 17, 2011

0

0.5

1

1.5

2

2.5

3

3.5

4

85 90 95 100 105 110 115 120 125 130 135 140 145

Ind

uc

tan

ce (μ

H)

Average of Magnet Input Face and Output Face Temperature During Cool down (˚C)

33 cells * 101nH/cell

106˚C

Magnet in vacuum tank; tank at atmospheric pressure; no bake-out jacket.

M.J. Barnes 14

Number of bunches for circulating beam include: Sat Apr 9th (50ns): 07:00hrs 12 + 4x72 circulating 10:24hrs 588 for both B1 & B2.

Sun Apr 10th (75ns): 11:44hrs 804 B1, 732 B2 17:27hrs 444 for both B1 & B2 17:46hrs 732 for both B1 & B2 18:05hrs 804 for both B1 & B2

23:51hrs 300 for both B1 & B2 Mon Apr 11th: 00:20hrs 804 B1, 732 B2 00:33hrs 804 for both B1 & B2 00:51hrs 876 for both B1 & B2 01:01hrs 948 for both B1 & B2 01:13hrs 1020 B1, 948 B2 01:19hrs 1020 for both B1 & B2

Temperature rises: Mag A Tube_up: dT = 19.0CMag A Tube_dn: dT = 5.9C Mag B Tube_up: dT = 25.6CMag B Tube_dn: dT = 10.3C Mag C Tube_up: dT = 27.4C Mag C Tube_dn: dT = 11.5C Mag D Tube_up: dT = 16.5C Mag D Tube_up: dT = 11.8C

Temperature rises: Mag A Ferrite_up: dT = 5.1CMag A Ferrite_dn: dT = N/A

Mag B Ferrite_up: dT = 5.8C Mag B Ferrite_dn: dT = 8.5C

Mag C Ferrite_up: dT = 6.2C Mag C Ferrite_dn: dT = 6.2C

Mag D Ferrite_up: dT = 5.8C Mag D Ferrite_dn: dT = 9.8C

31.2˚C (1020 bunches) 47.9˚C32

20 15

50

ALL MKI’s during cooldown:Max Tau 15.5hrsMin Tau 7.5hrsMax-Min Tau 8.0hrsMean Tau 11.7hrsSD Tau 2.3hrs

ALL Tubes during cooldown:Max Tau 7.9hrsMin Tau 3.7hrsMax-Min Tau 4.2hrsMean Tau 5.3hrsSD Tau 1.2hrs

Temperature Rise During Scrubbing

Notes: Magnet A, ferrite dn PT100 not working.Initial spread in temperatures ~2˚CAlmost 5˚C range of dT for magnets (of 9.8 ˚C max.). 21.5˚C range of dT for tubes (of 27.4 ˚C max.)Conclusion: thermal contacts are difficult – and big variation in readings results: hence start with low SIS.

LIBD: May 17, 2011

50ns

50ns

15

40

15

25

35

30

20

Magnet Heating: Measurements during Operation

D5R8_dn: 38.2˚C (extrapolated max. 39.5˚C, τ=8hrs)

B5R8_dn: 35˚C

B5L2_up: 29.2C

Wide range of magnet temperatures, and “up” & “down” can be quite different – poor thermal contact. Note: 38.2˚C (D5R8_dn) is the highest magnet temperature noted to date.

LIBD: May 17, 2011 M.J. Barnes

D5R8_dn: 37.5˚C (extrapolated max. 42.8˚C, τ=8hrs)D5R8_dn: 37.5˚C

16

Tube Heating: Measurements during Operation

B5R8_up: 51.1C

A5L2_up: 41.6C

Wide range of magnet temperatures, and “up” & “down” can be quite different – poor thermal contact. Note: 56.3˚C (C5R8_dn) is the highest tube temperature noted to date.

LIBD: May 17, 2011 M.J. Barnes

C5R8_up: 56.3˚C (extrapolated max. 59˚C, τ=2.5hrs)

17LIBD: May 17, 2011 M.J. Barnes

Magnet D5R8_dn & Tube C5R8_up Heating with Beam Intensity & Energy

37.5˚C Steady-State (Mag. D5R8_Dn) [5.8e13 charges]

9.7e13 charges

50.4˚C high (Tube C5R8_up) [5.8e13 charges]

Mag. D5R8_dn (3.5 TeV) ~15˚C rise, above 22 ˚C, with 5.8e13 charges & ~20˚C rise (extrapolated) with 9.7e13 charges.Tube C5R8_up (3.5 TeV) ~28˚C rise, above 22 ˚C, with 5.8e13 charges & ~37˚C rise (extrapolated) with 9.7e13 charges.Note: following energy ramp, during energy flattop, bunch length increases – hence probably reason for tube “cooling”.

M.J. Barnes 18Cryo problem at point 8: pressure increase to 2.1e-9mbar in MKI8’s. Q4 beam screen temp. is approx the average of the screen input and output temperatures.LIBD: May 17, 2011

MKI8-A pressure (2.1e-9 mbar max)

Magnet A-B interconnect

Q5 side of MKI8 magnet D

Q4 Screen output temp.

Q4 Screen input temp.

A B C D

Injected Beam

May 13, 2011: Cryogenic Temperature and MKI vacuum

M.J. Barnes 19

Sublimation: MKI8, May 2011

Sublimation on magnets C & D carried out 19 April 2011, following spark.Sublimation on all 4 MKI’s, at both points, carried out during TS of early May 2011.

LIBD: May 17, 2011

Cryo problem

Sublimation(Thurs 12/05/2011)

D

CBA

Cause ?: present near MKI’s too

M.J. Barnes 20

Summary of Experience with MKI’s Considerable vacuum activity around MKI’s during beam scrubbing – mainly from Q5 area. Ecloud solenoids close to MKIs now turned on (5A): but their effectiveness is now yet assessed; Total of 2 electrical breakdowns on MKI8-D (during SoftStarts) and total of 2 during injections (latest April 18, 2011); Total of 3 electrical breakdowns on MKI2-B (during injections) – hence magnet changed during Christmas stop; Pressure rise in MKI’s is normally during injection. During the slow pressure rise on 2 May 2011, there does not seem to be a correlation of vacuum pressure increase with: beam loss, cryogenics temperature or bunch length. However the cryogenics can have a big effect on the MKI pressure, Measurements in the clean room, on a single MKI, showed reduced inductance at 106˚C measured on magnet ground plate (with PT100); but there is a LARGE spread in temperature rises during operations (~2:1).

38.2˚C (D5R8_dn) is the highest magnet temperature noted to date in tunnel. SIS interlock, of magnet temperature, set to 55˚C.

Mean cool-down time-constants: magnet 11.7 hrs, σ=2.3hrs; tube 5.3 hours, σ=1.2hrs. Adequate time required for cool-down between before next coast! Sublimation is effective at reducing MKI pressure; ACOND/SOFTSTART: strong spark threshold now 1.2e-9mbar (originally 4e-9 mbar);

weak spark threshold now 8e-10mbar (originally 1e-9mbar); Vacuum interlock level: 2e-8 mbar (from late March 2011; before late March was 5e-8 mbar).

LIBD: May 17, 2011

M.J. Barnes 21

Future Plans Closely monitor vacuum activity around MKI’s and identify causes; Assess effectiveness of Ecloud solenoids close to MKI’s; Determine whether Ecloud solenoids need to be installed between MKI’s; Closely monitor MKI temperature and “performance” (e.g. deflection of beam and electrical performance of system [e.g. rise time of TMR current, delay of TMR current, transient increase of MS current];

Run PSpice models of MKI system with reduced magnet inductance and determine electrical parameters that could be used for IPOC interlock;

Thermally model MKI magnet and predict ferrite temperature (as per MKE’s) – but no one foreseen for this activity….;

Determine good setting for SIS interlock for magnet temperature. Study effect of BIRF ferrite heating to Curie temperature: do losses in magnet ferrite increase? (possibly make more measurements). MDs to determine ferrite temperature rises for various intensities and energies?? Sublimation may be used on a reasonably regular basis – procedure to be formulated.

LIBD: May 17, 2011