E. Todesco

MQXAB: DECAY AND FIELD HARMONICS

E. TodescoMagnets, Superconductors and Cryostats Group

Technology Department, CERN

FiDeL meeting, 26th May 2009

Ackowledgements: P. Schlabach, G. Velev

E. Todesco 24th May 2009 – Decay and harmonics in MQXB - 2

CONTENTS

Features and function in the machine, and available measurements for field harmonics

Field harmonicsAllowedNot allowed

Decay

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MQXB: FEATURES AND FUNCTION IN THE MACHINE

16 magnets making 8 Q2, on each side of the four interaction points

Design and manufacturingmade in the US

Two layer, four-blocks, graded coilFree-standing collars

Currents: Injection 716-776 A to give 13.2 – 14.3 T/mCollision 5 TeV: 8120 ACollision 7 TeV: 11380 A to give 205 T/m

Beam dynamics:Negligible at injection, critical at high field after squeeze

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Field harmonics: AVAILABLE MEASUREMENTS

What do we have today ?

‘Integral’ measurements:For all magnets, for every cold massValues at 4 currents namely ~injection (669 A), 5460 A, ~collision at 7 TeV (11345 A), ultimate (11923 A). Injection (716-776A) higher than what measured (669 A): goodTo be checked:

PrecycleWaiting time before making the measurement

‘Dcloop’ measurements:More current values, only for transfer function

Other informations from papers

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CONTENTS

Features and function in the machine, and available measurements for field harmonics

Field harmonicsAllowedNot allowed

Decay

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Field harmonics: ALLOWED

The MQXB are critical after the squeezeWe propose to set the model at high field exactly on the measured valuesGeometric set at value at 7 TeV

For the allowed b6, b10

b6 at 7 TeV is smaller than 0.1 units – very well optimized ! Negligible changes from 3.3 to 7 TeV:no need of different settings at 4-7 TeVAt injection, -1.5 unit of b6 and a very small additional spread (0.2 units)

b10 always negligible

b6 b10

Ave -1.52 0.05

Stdev 0.61 0.02

Ave 0.06 0.01

Stdev 0.36 0.01

Ave 0.07 0.02

Stdev 0.36 0.01

Ave 0.07 0.02

Stdev 0.36 0.01

Ave -1.67 0.04

Stdev 0.19 0.01

669 A

5460 A

11347 A

11925 A

669 A - 11347 A

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Field harmonics: ALLOWED

Geometric:One per magnetSet at the value at 7 TeV

First 3 cold masses had a lower value b6, then a correction has been done through shims [G. Velev et al., IEEE Trans. Appl. Supercon. 17 (2007) 1109]

DC magnetizationComputed on the data averaged over all magnets: one generic, to take into account of about -1.5 units

pqinjc

Cold mass b6 b10

1 -0.401 0.016

2 -0.309 0.019

3 -0.403 0.020

5 0.163 0.028

6 0.353 0.026

7 0.224 0.016

8 -0.012 0.044

9 0.218 0.020

10 0.372 0.029

11 0.398 0.031

12 0.181 0.023

13 0.309 0.019

15 0.427 0.018

16 0.220 -0.001

17 0.157 0.015

18 -0.231 -0.009

19 0.415 0.003

20 -0.859 0.030

Average 0.07 0.02

Stdev 0.36 0.01

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Field harmonics: NOT ALLOWED

The MQXB are critical after the squeezeWe propose to set the geometric on the measured value at 7 TeV

For the not allowedSmall systematic b4 of about 0.1 units – could be relevantAll the other systematic are very close to zero !Spread at injection is the same as at high field – this is strange: in general the spread at high field is smaller than at injection

Slight difference with data presented in [G. Velev et al., IEEE Trans. Appl. Supercon. 17

(2007) 1109], where one has a systematic a4 of about 0.2 unitsb 3 b 4 b 5 b 7 b 8 b 9 a 3 a 4 a 5 a 6 a 7 a 8 a 9

Ave -0.06 0.10 0.06 0.03 -0.02 0.00 -0.07 -0.16 -0.01 -0.01 -0.01 -0.03 0.00

Stdev 0.66 0.14 0.12 0.04 0.01 0.01 1.12 0.58 0.19 0.08 0.04 0.03 0.01

Ave 0.05 0.10 0.07 0.01 0.00 0.00 0.09 -0.10 0.02 -0.04 -0.01 -0.01 0.00

Stdev 0.61 0.14 0.11 0.03 0.01 0.01 1.00 0.51 0.17 0.10 0.04 0.03 0.01

Ave 0.06 0.12 0.09 0.01 -0.01 -0.01 0.08 -0.08 0.02 -0.08 0.00 -0.01 0.01

Stdev 0.61 0.14 0.13 0.04 0.01 0.01 0.99 0.52 0.18 0.19 0.04 0.03 0.01

Ave 0.09 0.12 0.09 0.01 -0.01 -0.01 0.08 -0.08 0.02 -0.07 -0.01 -0.02 0.00

Stdev 0.64 0.14 0.13 0.03 0.01 0.01 1.00 0.52 0.18 0.20 0.04 0.03 0.01

Ave -0.13 -0.02 -0.03 0.02 -0.01 0.01 -0.15 -0.08 -0.03 0.06 -0.01 -0.02 0.00

Stdev 0.25 0.05 0.09 0.02 0.01 0.01 0.37 0.16 0.07 0.18 0.01 0.03 0.01

669 A

5460 A

11347 A

669 A - 11347 A

11925 A

Average and stdev of ‘Integral’ data Average and stdev of ‘Integral’ data as presented by G: Velev et al in IEEE Trans. Appl. Supercon. 17 (2007) 1109

E. Todesco 24th May 2009 – Decay and harmonics in MQXB - 9

CONTENTS

Features and function in the machine, and available measurements for field harmonics

Field harmonicsAllowedNot allowed

Decay

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DECAY

Measurements:We have no data, and we base our analysis on the results reported by G. Velev et al.In FNAL they used a two-parameter log fit

We used the listed parameters in Velev paper to reconstruct dataAverage b6 decay after 1200 s is 1.7 units with a 0.4 units spread

No info on the TF from that paper

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DECAY

FiDeL fitWe use a double exponential fitThe fit error is negligible (0.02 units)The parameters d and have a very small spread (the exp fit looks pretty solid!)

We propose to neglect this component

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 200 400 600 800 1000 1200

b6 (u

nits

)Measurement (log fit)

FiDeL fit

Cold mass b6,1 ts c d Db6 at 1200 s

1 0.50 13.3 1.41 0.40 55 1.342 0.35 8.9 1.75 0.44 50 1.683 0.50 12.9 2.40 0.42 60 2.255 0.30 9.8 1.48 0.42 50 1.426 0.50 13.9 2.32 0.40 55 2.208 0.26 8.1 1.33 0.44 50 1.289 0.34 9.5 1.69 0.42 50 1.62

10 0.35 9.8 1.72 0.42 50 1.6511 0.33 8.7 1.66 0.44 50 1.5912 0.55 15.3 2.55 0.40 60 2.3813 0.35 9.3 1.75 0.42 50 1.6817 0.54 15.6 2.49 0.40 60 2.3219 0.23 7.6 1.20 0.44 50 1.15

Ave 0.39 11.0 1.83 0.42 53 1.7Stdev 0.11 2.8 0.46 0.02 4 0.4

Exponential fit parametersLog fit parameters

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CONCLUSIONS

Geometric: set on values at collision (about 7 TeV), one component per magnet

b6 very well optimized (shimming from the fourth magnet to correct 0.5 units, final average within 0.1 units)Negligible difference from 5 to 7 TeVSmall systematic b4 (0.1 units)

Small systematic a4 (0.2 units) present in Velev papers, but not in our data – to be checked with FNAL colleagues

Persistent: about -1.5 unit on b6, taken into account by a persistent component, the same for every magnet

Decay: about 1.7 units on b6

Fit for b6 has been computed as an excercise, but we propose to neglect it in FiDeL

Anyway, it would be good to recover warm measurements, Dcloop, and decay