Vyacheslav Klyukhin, SINP MSU The CMS Magnetic Field Map Aug 7, RDMSV. Klyukhin, SINP MSU1

Outlook Aug 7, RDMSV. Klyukhin, SINP MSU2 The CMS detector The CMS magnet TOSCA model The CMS magnet model validation Conclusions

Compact Muon Solenoid - CMS Aug 7, RDMSV. Klyukhin, SINP MSU3

The CMS Magnetic System Aug 7, RDMSV. Klyukhin, SINP MSU4 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 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 Aug 7, RDMSV. Klyukhin, SINP MSU5 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 Aug 7, RDMSV. Klyukhin, SINP MSU6 HCAL ECAL Tracker HF Muon chambersUpgraded 4 th 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 Aug 7, RDMSV. Klyukhin, SINP MSU7 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 4 th Disks Aug 7, RDMSV. Klyukhin, SINP MSU8

The CMS Magnet Model Used for Validation Outer diameter is 14 m; full length of the barrel and end-cap yoke is 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. Aug 7, RDMSV. Klyukhin, SINP MSU9 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 Aug 7, RDMSV. Klyukhin, SINP MSU10 Barrel steel, forward parts End-cap steel

Magnetic Flux Distribution in the CMS Longitudinal Section Calculated with the Magnet Model Aug 7, RDMSV. Klyukhin, SINP MSU11

Magnetic Field Map Azimuth Sector Volumes Aug 7, RDMSV. Klyukhin, SINP MSU12

Magnetic Flux Distribution in the Middle Plane Calculated with the CMS Magnet Model Aug 7, RDMSV. Klyukhin, SINP MSU13 Selected and changed to R<50 m, |Z|<60 m in the recent model

Magnetic Field Map of 2014 Aug 7, RDMSV. Klyukhin, SINP MSU14 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

Calculated (2014) Magnetic Flux Density B x - component in the vertical plane at B 0 =3.81 T Aug 7, RDMSV. Klyukhin, SINP MSU15

Calculated (2014) Magnetic Flux Density B y - component in the horizontal plane at B 0 =3.81 T Aug 7, RDMSV. Klyukhin, SINP MSU16

The CMS Inner Field Measuring Aug 7, RDMSV. Klyukhin, SINP MSU17 In 2006 during the MTCC the magnetic field was measured with a fieldmapper designed and produced at Fermilab inside a cylinder of 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 m, the most inner Hall sensors are at 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 Aug 7, RDMSV. Klyukhin, SINP MSU18

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. Aug 7, RDMSV. Klyukhin, SINP MSU19

Magnetic Flux Density Measured with Hall sensors Near the CMS Coil Axis at B 0 =4.01 T Aug 7, RDMSV. Klyukhin, SINP MSU20 Magnetic flux density measured with Hall sensors at radius 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 B 0 =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.

Measured and Calculated (2009) Magnetic Flux Density at the coil axis for B 0 =4.01 T Aug 7, RDMSV. Klyukhin, SINP MSU21

Measured and Calculated (2009) Magnetic Flux Density the coil axis for B 0 =4.01 T Aug 7, RDMSV. Klyukhin, SINP MSU22 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).

Measured and Calculated (2014) Magnetic Flux Density at the coil axis for B 0 =4.01 T Aug 7, RDMSV. Klyukhin, SINP MSU23

Measured and Calculated (2009) Magnetic Flux Density the coil axis for B 0 =4.01 T Aug 7, RDMSV. Klyukhin, SINP MSU24 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).

Measured and Calculated (2009) Magnetic Flux Density at R=0.092 m for B 0 =4.01 T Aug 7, RDMSV. Klyukhin, SINP MSU25

Measured and Calculated (2009) Magnetic Flux Density at R=0.092 m for B 0 =4.01 T Aug 7, RDMSV. Klyukhin, SINP MSU26 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).

Measured and Calculated (2014) Magnetic Flux Density at R=0.092 m for B 0 =4.01 T Aug 7, RDMSV. Klyukhin, SINP MSU27

Measured and Calculated (2014) Magnetic Flux Density at R=0.092 m for B 0 =4.01 T Aug 7, RDMSV. Klyukhin, SINP MSU28 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).

Measured and Calculated (2009) Magnetic Flux Density at R=1.724 m for B 0 =4.01 T Aug 7, RDMSV. Klyukhin, SINP MSU29

Measured and Calculated (2009) B at R=1.724 m for B0=4.01 T Aug 7, RDMSV. Klyukhin, SINP MSU30 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).

Measured and Calculated (2014) Magnetic Flux Density at R=1.724 m for B 0 =4.01 T Aug 7, RDMSV. Klyukhin, SINP MSU31

Measured and Calculated (2014) B at R=1.724 m for B0=4.01 T Aug 7, RDMSV. Klyukhin, SINP MSU32 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).

The CMS Current Cycles in August 2006 Test Aug 7, RDMSV. Klyukhin, SINP MSU kA kA The CMS magnet operational current is kA

Location of Flux Loops and Immovable Hall sensors Aug 7, RDMSV. Klyukhin, SINP MSU34

Flux loops description Aug 7, RDMSV. Klyukhin, SINP MSU35 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 Aug 7, RDMSV. Klyukhin, SINP MSU36

Magnetic Flux Density at Y= ‒ 4.805, ‒ 5.66, and ‒ m (17.55 kA) Aug 7, RDMSV. Klyukhin, SINP MSU37

Magnetic Flux Density at Y= ‒ 4.805, ‒ 5.66, and ‒ m (19.14 kA) Aug 7, RDMSV. Klyukhin, SINP MSU38

Comparison of Calculation and Measurements Aug 7, RDMSV. Klyukhin, SINP MSU39 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 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 kA The error bars of the 3-D Hall sensor measurements are ± (0.025±0.015) mT at the current of kA and ± (0.012±0.001) mT at the current of 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 Aug 7, RDMSV. Klyukhin, SINP MSU40 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 Aug 7, RDMSV. Klyukhin, SINP MSU41

Aug 7, RDMSV. Klyukhin, SINP MSU42

Central Magnetic Flux Density Measured with the NMR-Probes vs. CMS Coil Current Aug 7, RDMSV. Klyukhin, SINP MSU43

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 to 2.55 m the measurements have been performed twice. Aug 7, RDMSV. Klyukhin, SINP MSU44

“Fast” Discharges of the CMS Coil Aug 7, RDMSV. Klyukhin, SINP MSU kA kA 15.0 kA 12.5 kA The CMS magnet working current in present time is kA

Voltages Induced in the W-1 blocks and the Integrated Magnetic Flux Densities Aug 7, RDMSV. Klyukhin, SINP MSU46 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.

Magnetic Flux Density at Y= ‒ 5.66 m Aug 7, RDMSV. Klyukhin, SINP MSU47

Magnetic Flux Density at Z= ‒ m Aug 7, RDMSV. Klyukhin, SINP MSU48