Power Tracking Test Results

27th July 2007

Power Tracking Test Results

N. Sammut

And inputs from W. Venturini, L. Bottura, S.Sanfilippo,

L. Walckiers, S.Bouchenoua, G.Deferne, J. Miles, R. Mompo

AB-OP

With several inputs from M. Lamont, M. Strzelczyk

27th July 2007 Power Tracking Test Results N. Sammut

Postponed due to cryo limitation

Test Program

Not performed due to problems in 3)


1st Result

-2

-1.5

-1

-0.5

0

0.5

25/06/1900

00:00:00

15/07/1900

00:00:00

04/08/1900

00:00:00

24/08/1900

00:00:00

13/09/1900

00:00:00

03/10/1900

00:00:00

23/10/1900

00:00:00

12/11/1900

00:00:00

02/12/1900

00:00:00

t (s)

co

mp

en

sa

ted

b3

(u

nit

s)

Ap2


-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

04/07/190000:00:00

23/08/190000:00:00

12/10/190000:00:00

01/12/190000:00:00

20/01/190100:00:00

11/03/190100:00:00

time (s)

com

pen

sate

d b

3(u

nit

s)

2nd Result – after parameter readout error detected

Ap1


-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0 10 20 30 40 50 60 70 80 90

t (s)

b3

(un

its)

Hmm – indication that problem lies with static model

b3 compensation of a cycle without decay and snapback


-7.2

-7

-6.8

-6.6

-6.4

-6.2

-6

-30 -10 10 30 50 70 90 110 130 150 170

t (s)

b3

(un

its)

standard lhc cycle 50A/s standard lhc cycle 10A/s no correctors tracking test

loadline data (50 A/s) Model prediction loadline data 10a/s

Hmm – pre-cycle ramp rate effects the loadline?


-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

-500 0 500 1000 1500 2000 2500 3000 3500 4000

t (s)

b3

(un

its)

calculated error from calibration curve compensation due to ramp rate dependence

Ramp rate effect compensation


3rd Result – after loadline compensation for ramp rate dependence

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0 20 40 60 80 100

t(s)

b3

(u

nit

s)

co

mp

en

sa

ted

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0 500 1000 1500 2000 2500

I(A)

b3

(u

nit

s)

co

mp

en

sa

ted

Ap2


-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0 2000 4000 6000 8000 10000 12000 14000

I (A)

res

mag

an

d s

at b

3 (u

nit

s)

loadline resmag and sat data new model old model

Hmm – the residual magnetisation model needs to be improved?


-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

100 120 140 160 180 200 220 240 260

t (s)

com

pen

sate

d b

3 (u

nit

s)

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0 200 400 600 800 1000 1200 1400 1600 1800

I (A)

com

pen

sate

d b

3 (u

nit

s)

4th Result – after loadline compensation for ramp rate dependence and change of residual magnetisation model

Ap2


Hmm – are we suffering from lack of granularity in standard loadline measurement?

-8

-7

-6

-5

-4

-3

-2

-1

0

0 1000 2000 3000 4000 5000 6000

I (A)

b3

(u

nit

s)

data ramp up model ramp up


Hmm – are we suffering from lack of granularity in standard loadline measurement?

Measurements without pre-cycle ramp rate compensation

raw data

-8

-6

-4

-2

0

2

4

6

8

0 2000 4000 6000 8000 10000 12000

I (A)

b3

(un

its)

long loadline data (50A/s) characterisation loadline data (50A/s)


-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0 2000 4000 6000 8000 10000 12000 14000

I(A)

b3

res

mag

sat

(un

its)

Series1

Series2

Long injection residual magnetization artifact


5th Result – after loadline compensation for ramp rate dependence and change of residual magnetisation model and increased points for loadline

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0 20 40 60 80 100 120

t (s)

com

pen

sate

d b

3 (u

nit

s)

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0 200 400 600 800 1000 1200 1400 1600 1800

I (A)

b3

(un

its)


-0.1

-0.05

0

0.05

0.1

0.15

0 2000 4000 6000 8000 10000 12000 14000

I (A)m

od

el v

s d

ata

erro

r b

3 (u

nit

s)

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0 200 400 600 800 1000 1200 1400 1600 1800

I (A)

b3

(un

its)

Hmm – Lets compare model error to b3 compensation

b3 compensation Model error

Snapback error?

Hysteresis error?


-8

-7.5

-7

-6.5

-6

-5.5

-5

-4.5

-4

700 750 800 850 900 950 1000 1050 1100

characterisation loadline data (50A/s)loadline data with ramp rate compensation (50A/s)loadline MODEL ramp rate compensation and with new model (50 A/s)machine cycle PTT no correctors (10A/s)loadline MODEL ramp rate compensation and with new model (50 A/s)long loadline ramp compensated (50 A/s)standard load line 26th July (50 A/s)long loadline data (50A/s)

What if we model the static on the LHC cycle that we get when correctors are switched off?

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0 20 40 60 80 100 120

t (s)

b3

com

pen

sate

d (

un

its)

This indicates that it is probably snapback and/or corrector hysteresis


Open issue 1 – Is loadline reproducible?

data

-6

-5.8

-5.6

-5.4

-5.2

-5

-4.8

-4.6

-4.4

-4.2

-4

950 970 990 1010 1030 1050

I (A)

b3

(u

nit

s)

characterisation loadline data (50A/s)standard load line 26th July (50 A/s)long loadline data (50A/s)machine cycle PTT no correctors (10A/s)

For long cycle maybe there is an effect of powering history (though decay compensation is proportional to difference in two loadline points)


Open Issue 2 - Does the Fixed Gain effect ?

Dipole on at injection current, corrector on at ~ 50A

Sector 00-01

Gain = 2 (200comp)

Gain = 0.1 (20comp)

121.35

121.4

121.45

121.5

121.55

121.6

(-)

b3

(un

its)

Warning: might not be a reliable measurement

Should points be inverted?


-0.04800

-0.04700

-0.04600

-0.04500

-0.04400

-0.04300

-0.04200

-0.04100

-0.04000

-0.03900

0 100 200 300 400 500 600

Open Issue 3 – Variation of measured sextupole with Shaft position

Feed down error maybe?


Open Issue 4 – What is the effect of the corrector hysteresis?

-0.001

-0.0008

-0.0006

-0.0004

-0.0002

0

0.0002

0.0004

0.0006

0.0008

0.001

0 100 200 300 400 500 600

I (A)

b3

(T

m/k

A)

data ramp up data ramp down


Other considerations

1) Is timing wrong? 1s = 0.015units of b3 change in dipole

2) Snapback correlation might be different for this magnet

3) Snapback correlation might be affected by the loadline not being reproducible. (Also loadline was not compensated for ramp rate)


Proposal

1) Fix Shafts that have problems with sectors

2) Perform detailed loadline on each magnet (including SSS) (debug cycle)

3) Investigate well the difference in loadline measurements

4) Investigate effect of fixed gains and preferably have system with variable gains

5) Investigate variation of sextupole with shaft position

6) Perform detailed hysteresis measurements of all corrector types and investigate importance of this effect

7) Investigate timing

8) Find better fit for Residual Magnetisation

9) Maybe also investigate decay as a function of injection current

10) System such that current is saved in measurement entries (ease analysis considerably)

11) Use FAME for next measurement after a detailed characterisation and cross calibration of the instrument

12) Perform snapback measurement using Hall probe too

Documents

Power Tracking Test Results