vyacheslav klyukhin, sinp msu

Vyacheslav Klyukhin, SINP MSU

New CMS Magnetic Field Map

May 26, 2014 - GMM V. Klyukhin, SINP MSU / CERN 1

2

Outlook

May 26, 2014 - GMM V. Klyukhin, SINP MSU / CERN

• The CMS detector• The CMS magnet TOSCA model• The CMS magnet model validation• Conclusions

V. Klyukhin, SINP MSU / CERN 3

Compact Muon Solenoid - CMS

May 26, 2014 - GMM


The CMS Magnetic System

May 26, 2014 - GMM

• The Compact Muon Solenoid (CMS) is a general purpose detector at the CERN Large Hadron Collider (LHC)

• The CMS magnetic system consists of 4T NbTi superconducting coil with 6 m diameter by 12.5 m long free bore and a 10000-ton yoke made of construction steel (up to 0.17% C, up to 1.22% Mn, some Si, Cr, and Cu)

• The yoke includes 5 dodecagonal 3-layred barrel wheels, 4 end-cap disks at each end, 2 nose disks and comprises the ferromagnetic parts of forward hadronic calorimeter and the LHC magnets shield


The CMS Transverse Section in the Middle Plane

May 26, 2014 - GMM

12 azimuth sectors, S

2 chimneys for electrical and cryogenic leads

Steel connecting brackets

Tail catcher rotated by 5º w. r. t. the barrel blocks

Muon chambers

Barrel feet

HCAL, ECAL,tracker


The CMS One Quarter Longitudinal Section

May 26, 2014 - GMM

HCALECAL

Tracker

HF

Muon chambers Upgraded 4th disk

The contribution of the yoke central part into the central magnetic flux density is 7.97%. The contribution of the forward parts and the steel floor of the underground experimental cavern is 0.03%.


The CMS Magnet Model

May 26, 2014 - GMM

• The continuous direct measurements of the magnetic flux density B have been performed in the inner tracker region

• The continuous direct measurements of B outside the CMS coil are extremely difficult to perform

• The description of B distribution in full detector volume is done with a 3-D model of the CMS magnetic system calculated with the Cobham / Vector Fields program TOSCA

• The model validation is done with the 3-D Hall sensor and flux loop measurements


The CMS Magnet Model with Upgraded 4th Disks

May 26, 2014 - GMM


The CMS Magnet Model Used for Validation

Outer diameter is 14 m; full length of the barrel and end-cap yoke is 21.61 m; the coil inner bore is 6 m, the coil length is 12.5 m, the operational central magnetic flux density is 3.81 T.

May 26, 2014 - GMM

Carts

5 barrel wheels, W

Nose disk, N

Tail catcher, TC

Superconducting solenoid of 4 T 4 end-cap discs,

D

Keels

Chimney at W+1

The B-H Curves Used in the Model


Barrel steel, forward parts

End-cap steel


Magnetic Flux Distribution in the CMS Longitudinal Section Calculated with the Magnet Model

May 26, 2014 - GMM


Magnetic Field Map Azimuth Sector Volumes

May 26, 2014 - GMM


Magnetic Flux Distribution in the Middle Plane Calculated with the CMS Magnet Model

May 26, 2014 - GMM

Selected and changed to R<50 m, |Z|<60 m in the recent model


Magnetic Field Map of 2014

May 26, 2014 - GMM

• Map is prepared in a cylinder of 18 m diameter and

40 m long• 9600 volumes are used in the full azimuth range• The volumes boundaries correspond to field discontinues, which are due to changes in magnetic permeability of the materials• The volumes are grouped in 24 azimuth sectors

and searching is made for 400 volumes in the needed sector• Cashing mechanism reduces the CPU time of

searching• B in a given point is found by linear interpolation between the values on a regular grid• The necessary tables of B are prepared with the OPERA-3d Post-Processor tool using scripts

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Calculated (2014) Magnetic Flux Density Bx-component in the vertical plane at B0=3.81 T


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Calculated (2014) Magnetic Flux Density By-component in the horizontal plane at B0=3.81

T



The CMS Inner Field Measuring

May 26, 2014 - GMM

In 2006 during the MTCC the magnetic field was measured with a fieldmapper designed and produced at Fermilab inside a cylinder of 1.724 m radius and 7 m length at 5 central field values: 2, 3, 3.5, 3.8, and 4 T.The radial distance between 3-D Hall sensors is 0.408 m, the most inner Hall sensors are at 0.092 m off the coil axis.

3-D Hall sensors

NMR-probe


3-D Hall sensors developed at NIKHEF (Netherlands)

• selection by single Chip-Select signal

• module identification by 64-bit ID-chip

• readout/control by SPI (Serial Peripheral Interface)

• used in ATLAS and CMS

May 26, 2014 - GMM


The Hall sensors Calibration at GHMFL(Grenoble, France)

The Hall sensor calibration is done at 4.5, 3.5, and 2.5 T field on May 30 − June 3, 2005 inside the 130 mm bore resistive magnet M5 in GHMFL at Grenoble with relative accuracy of 5∙10−4.

May 26, 2014 - GMM


Magnetic Flux Density Measured with Hall sensors Near the CMS Coil Axis at B0=4.01 T

May 26, 2014 - GMM

Magnetic flux density measured with Hall sensors at radius 0.092 m along the coil axis in the range of ±3.5 m with respect to the coil transverse middle plane in full azimuth coverage at B0=4.01 T central filed.

Averaging for each Z-coordinate over the full range of azimuth angle gives typical standard deviation of 4·10-5 T.

The general precision of the measurements is 7·10-4.

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Measured and Calculated (2009) Magnetic Flux Density at the coil axis for B0=4.01 T



Measured and Calculated (2009) Magnetic Flux Density the coil axis for B0=4.01 T

May 26, 2014 - GMM

The measurements performed at R=0 m with NMR probe located on the coil axis in the middle of the fieldmapper (filled markers) differ from the calculated values (magenta curve) by 3.6±1.2mT (opened markers).

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Measured and Calculated (2014) Magnetic Flux Density at the coil axis for B0=4.01 T



Measured and Calculated (2009) Magnetic Flux Density the coil axis for B0=4.01 T

May 26, 2014 - GMM

The measurements performed at R=0 m with NMR probe located on the coil axis in the middle of the fieldmapper (filled markers) differ from the calculated values (magenta curve) by 2.4±1.3mT (opened markers).

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Measured and Calculated (2009) Magnetic Flux Density at R=0.092 m for B0=4.01 T




May 26, 2014 - GMM

The measurements performed at R=0.092 m with Hall sensor located on the negative fieldmapper arm (thick blue curve) differ from the calculated values (dashed red curve) by 2.1±2.0 mT (light blue square dots).

The measurements performed at R=0.092 m with Hall sensor located on the positive fieldmapper arm (thin green curve) differ from the calculated values (dashed red curve) by 1.4±1.6 mT (light green round dots).

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May 26, 2014 - GMM

The measurements performed at R=0.092 m with Hall sensor located on the negative fieldmapper arm (thick blue curve) differ from the calculated values (dashed red curve) by 0.4±2.3 mT (light blue square dots).

The measurements performed at R=0.092 m with Hall sensor located on the positive fieldmapper arm (thin green curve) differ from the calculated values (dashed red curve) by ‒0.3±1.9 mT (light green round dots).



May 26, 2014 - GMM


Measured and Calculated (2009) B at R=1.724 m for B0=4.01 T

May 26, 2014 - GMM

The measurements performed at R=1.724 m with NMR probe located on the negative fieldmapper arm (blue rhombs) differ from the calculated values (red curve) by 4.0±1.0 mT (gold triangles).

The measurements performed at R=1.724 m with Hall sensor located on the negative fieldmapper arm (blue open squares) differ from the calculated values (red curve) by 2.9±2.2 mT (gold slanted crosses).

The measurements performed at R=1.724 m with Hall sensor located on the positive fieldmapper arm (blue open circles) differ from the calculated values (red curve) by 3.5±1.4 mT (gold right crosses).



May 26, 2014 - GMM


Measured and Calculated (2014) B at R=1.724 m for B0=4.01 T

May 26, 2014 - GMM

The measurements performed at R=1.724 m with NMR probe located on the negative fieldmapper arm (blue rhombs) differ from the calculated values (red curve) by 1.4±0.7 mT (gold triangles).

The measurements performed at R=1.724 m with Hall sensor located on the negative fieldmapper arm (blue open squares) differ from the calculated values (red curve) by 1.4±0.7 mT (gold slanted crosses).

The measurements performed at R=1.724 m with Hall sensor located on the positive fieldmapper arm (blue open circles) differ from the calculated values (red curve) by 1.4±0.7 mT (gold right crosses).

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The CMS Current Cycles in August 2006 Test


17.55 kA 19.14 kA

The CMS magnet operational current is 18.164 kA


Location of Flux Loops and Immovable Hall sensors

May 26, 2014 - GMM


Flux loops description

May 26, 2014 - GMM

• 22 flux loops are performed from the flat ribbon cable of 45 wires that has been wound 7÷10 times around 12 blocks of W0, W-1, W-2, D-1, and D-2 at the bottom 30º or 18º azimuth sectors

• The areas enclosed by the flux loops vary from 0.31 to 1.59 m² on the barrel wheels and from 0.5 to 1.13 m² on the end-cap disks

• The voltages read out with seven DAQ modules USB-1208LS of Measurement Computing with 4 differential 12-bit analog inputs

• The DAQ modules are attached by the USB cables to two network-enabled AnywhereUSB®/5 hubs connected to PC through 3Com® OfficeConnect® Dual Speed Switch 5 sitting on local Ethernet cable of 90 m.


Hall Sensors Used for Validation

May 26, 2014 - GMM

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Magnetic Flux Density at Y= ‒4.805, ‒5.66, and ‒6.685 m (17.55 kA)


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Magnetic Flux Density at Y= ‒4.805, ‒5.66, and ‒6.685 m (19.14 kA)



Comparison of Calculation and Measurements

May 26, 2014 - GMM

• Total uncertainty of the flux loop measurements is 8.55% and includes the errors in the knowledge of the flux loops geometries and the errors of measured flux of (1.5±1.5)%

• The calculated values differ from the measures B by (0.59±7.41)% in the barrel wheels and (‒4.05±1.97)% in the end-cap disks at the current of 17.55 kA

• The calculated values differ from the measures B by (1.41±7.15)% in the barrel wheels and (‒2.87±2.00)% in the end-cap disks at the current of 19.14 kA

• The error bars of the 3-D Hall sensor measurements are ± (0.025±0.015) mT at the current of 17.55 kA and ± (0.012±0.001) mT at the current of 19.14 kA in average

• The model perfectly describes the magnetic flux density distribution inside the CMS coil within 0.1% in accordance with the previous model


Conclusions

May 26, 2014 - GMM

• The new CMS magnet model is developed to prepare the magnetic field maps for the upgraded CMS detector. The model is validated by the comparison of the calculated magnetic flux density with the measurements done in the CMS magnet selected regions with the flux loops and 3-D Hall sensors.


BACKUP

May 26, 2014 - GMM

V. Klyukhin, SINP MSU / CERN 42May 26, 2014 - GMM

Central Magnetic Flux Density Measured with the NMR-Probes vs. CMS Coil Current

B (T) vs. current (A) at R=2.9148 m

y = 0.0002148x + 0.0175637R2 = 0.9999949

y = 0.0002084x + 0.0170442R2 = 0.9999949

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 5000 10000 15000 20000 25000

Current, A

B, T

B at R=2.9148 m, T B at center, TLinear (B at R=2.9148 m, T) Linear (B at center, T)



The CMS Inner Volume Measured Field Map

The field map is measured on a mesh of 48 ΔØ = 7.5 degree (+1) steps x 140 ΔZ = 5 cm (+1) steps 4 x ΔR = 408 mm (+1) steps within |Z|<3500 mm, R<1724 mm with 10 Hall sensors and 2 NMR probes (at R=0 and R=1724 mm) at 2, 3, 3.5, 3.8, and 4 T central field.

The distance in Z between the Hall sensors located on positive and negative fieldmapper arms is 0.95 m and in the range of Z from -2.55 to 2.55 m the measurements have been performed twice.

May 26, 2014 - GMM

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“Fast” Discharges of the CMS Coil


19.14 kA17.55 kA

15.0 kA

12.5 kA The CMS magnet working current in present time is 18.164 kA

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Voltages Induced in the W-1 blocks and the Integrated Magnetic Flux Densities


Voltages

Integrated Magnetic Flux Densities

The voltages induced in the flux loops during “fast” (190 s time constant) discharges of the CMS coil have been integrated off-line with time for at least 1300 s.

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Magnetic Flux Density at Y= ‒5.66 m


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Magnetic Flux Density at Z= ‒7.565 m


vyacheslav klyukhin, sinp msu

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