Magnetic requirements for the commissioning
description
Transcript of Magnetic requirements for the commissioning
Magnetic requirements for the commissioning
E. Todesco
Accelerator Technology DepartmentMagnet and Superconductors Group
Acknowledgements: the speakers, S. Ramberger, J. P. Koutchouk
CERN, 10th February 2006
Chamonix summing up
February 10 2006 E. Todesco AT-MAS-MA 2
Magnetic requirements for commissioning
85% of the main dipole coils and 100% of the main quadrupole coils have been wound and assembled
What has been done is done …
Activities related to magnet performances and field quality are shifting
from the follow-up of the production, and corrective actionsto gather all the knowledge that could be useful for the commissioning
Introduction
-2
0
2
4
6
8
10
0 100 200 300 400 500 600 700
Aperture progressive number
b6 in
tegr
al w
ith n
omin
al µ
r (u
nits
)
upper target systematicsystematic
AT-MAS
lower target systematic
cross-section 1 cross-section 2
Main quadrupoles
-15
-10
-5
0
5
10
0 100 200 300 400 500 600 700 800 900 1000Collared coil progressive number
b3 in
tegr
al (
units
)
Firm 1
Firm 2
Firm 3
Collared coil
upper limit for systematic
lower limit for systematic
X-section 3
AT-MAS & MTM
X-section 2
Main dipoles
February 10 2006 E. Todesco AT-MAS-MA 3
Magnetic requirements for commissioning
Behavior of magnets for operationOrbit, tune and chromatic correctors (R. Steinhagen, W. Venturini)Dynamic effects for the field model (M. Lamont)
Estimating quantities relevant for commissioningBeta-beating (S. Sanfilippo)Quench level without beam (P. Pugnat)
OtherMEB activities (L. Bottura)Parasitic fields estimates (A. Devred)
Structure of the session
February 10 2006 E. Todesco AT-MAS-MA 4
Magnetic requirements for commissioning
With a pre-cycle 0A – 55A – 0 AThe remenant field corresponds to a kick of 0.560.05 rad
Both systematic and random effects are within tolerances
No need of a degaussing cycle to set the systematic to zero
Hysteresis in orbit correctors (R. Steinhagen)
Feedback correctionSmall loops are giving an hysteresis which does not affect the feedback algorithm
Measurements at Block4 by W. Venturini et al.
February 10 2006 E. Todesco AT-MAS-MA 5
Magnetic requirements for commissioning
Tune correctors (MQT)It would be better to operate them at small, non-zero current (1.5% of max corresponds to 0.2 of detuning)Global hysteresis gives a detuning of 0.005Decay of b2 gives 0.01 of detuningA correction with a linear model gives an uncorrected detuning of 0.0015 Hysteresis can be ignored
Hysteresis in tune and chromatic correctors (W. Venturini)
Chromatic correctorsSmall loops are giving an hysteresis which does not affect the feedback algorithm
0.00E+00
1.00E-03
2.00E-03
3.00E-03
4.00E-03
5.00E-03
6.00E-03
7.00E-03
8.00E-03
9.00E-03
1.00E-02
0 1 2 3 4 5 6 7 8Current (A)
Inte
grat
ed B
2 (T
m @
17m
m)
-1.0E-03
-5.0E-04
0.0E+00
5.0E-04
1.0E-03
1.5E-03
-20 -15 -10 -5 0 5 10 15
Current (A)
MC
S B
3 i
nte
gra
l (
Tm
@1
7 m
m)
February 10 2006 E. Todesco AT-MAS-MA 6
Magnetic requirements for commissioning
Field model (FiDeL)Magnetic measurements fitting procedure and extraction of model parameters (by N. Sammut, L. Bottura, J. Micallef)
Slot allocation evaluation of the behavior of magnets connected to the same power supply
DeliverablesSector test
Transfer function of MB, MQ, correctorsDecay predictionCycling prescription
CommissioningEverything for sector test plus snapback
Field model deliverables (M. Lamont et al)
I
ItIsnapback
injection
ebtb
33
Example of snapback fit
February 10 2006 E. Todesco AT-MAS-MA 7
Magnetic requirements for commissioning
Beta-beating:Error in the optic functions due to imperfections (mainly on the quadrupole strength)It reduces the mechanical aperture for the beamThe budget is 21% of maximum beta-beating
Estimates of beta-beating (S. Sanfilippo et al)
Previous experienceBeta-beating in LEP was 200% at the beginning of commissioning
LTC asked for estimates: are imperfections under control ?
Previous workDifferent sources of beta-beating have been identified
Targets/estimates based on the early production have been given
February 10 2006 E. Todesco AT-MAS-MA 8
Magnetic requirements for commissioning
New estimate:Based on measured values, slot allocation, estimated precision of measurement systems (by P. Hagen, J. P. Koutchouk, M. Giovannozzi, T. Risselada)
Effect of cell MQ, of MB, and of individually powered MQ taken into account Feed down due to misalignment still relies on estimates – measurements will be included soon
Results within target
Estimates of beta-beating (S. Sanfilippo et al)
February 10 2006 E. Todesco AT-MAS-MA 9
Magnetic requirements for commissioning
Available data908 main dipoles tested, 115 with a 2nd thermal cycle196 main quadrupoles, 9 with a 2nd thermal cycle
Statistical analysis to guess how many quenches are needed to work at 7 TeV
25-306 quenches per octant in the dipoles (depending on detraining), with a two sigma error86 quenches per octant in the quadrupoles, with a two sigma error
Expected quench level without beam (P. Pugnat)
February 10 2006 E. Todesco AT-MAS-MA 10
Magnetic requirements for commissioning
Magnet Evaluation Board activity is at full speed1/2 of the dipoles and 1/3 of the quadrupoles allocatedMixing of dipole manufacturers in sectors
Small systematic differences in field quality between firms
The same inner cable in the same sector (when possible)
Criteria (S. Fartoukh et al.)
Geometry maximizing mechanical aperture
Field qualityMinimizing σ(b1) in dipoles (avoid eating the orbit correctors budget)Minimizing σ(b2) in quadrupoles (beta-beating, mechanical aperture)Minimizing σ(b3) in dipoles (3rd order resonance, dynamic aperture)
What we gained with sorting (L. Bottura)
February 10 2006 E. Todesco AT-MAS-MA 11
Magnetic requirements for commissioning
Geometry Dipole allocation taking into account the actual beam dimension (worse magnets in mid half-cell positions)Quadrupole installation with tilts and rolls in a few cases to maximize mechanical aperture
What we gained with sorting (L. Bottura)
Field qualityb1 sorting used for the early phase of production (first sector)In the first sector, random b3 was 15% larger than target
sorting allowed to stay within targets (improvement by a factor 3 !)
Sorting still used to further improve random b3 (you never know …)
installation with tilt and roll
What we would get with nominal installation
February 10 2006 E. Todesco AT-MAS-MA 12
Magnetic requirements for commissioning
Beam screenNew analysis of the measurements at block4 (W. Venturini) show agreement with simulations (B. Auchmann)
Smaller effect on b5, b7 can be due to misalignment
Chasing parasitic fields (A. Devred)
Connection cryostatPbSb plates in the connection cryostat can become superconductive and quench
Kick on the beam well above specificationSolution: add a thermal link to keep “warm” the PbSb (above Tc) (A. Poncet et al.)
Effect of bus-bars3d models have been built, (B. Auchmann) field and impact on the beam is being evaluated (C. Vollinger, J. P. Koutchouk)
February 10 2006 E. Todesco AT-MAS-MA 13
Magnetic requirements for commissioning
Future outlookOptimize the magnetic measurements activities to get as much information as possible(Production follow-up is less critical now)
Dynamic components of main quadrupoles
Transfer function of special quadrupoles
Statistics on the dynamic components of dipoles
Characterization of all correctors (cycles, feedback)
Translate the magnetic and geometric measurements into a model of the machine
Including the slot allocation
Start estimating the relevant quantities for the beamTF for MB and MQ, detuning, natural chromaticity, (resonances)
Different TF and corrector settings for octants
Be ready for the first benchmark with the beam