Elena.Litvinenko CBM Collaboration Meeting Dubna 17 Oct 2008 1

Dipole magnet for CBM: current status

P.G. Akishin, A.V. Alfeev, V.S. Alfeev, V.V. Borisov,

V.V. Ivanov, E.I. Litvinenko, A.I. Malakhov,

E.A.Matyushevskiy

JINR, Dubna

Elena.Litvinenko CBM Collaboration Meeting Dubna 17 Oct 2008 2

The task definition

The main task is to provide the design of a magnet with:• the working angular acceptance at least of 50° for the

height of a gap (1.2 m) and 60° for the width of a gap (1.4 m), and, for the mounting inside the gap MVD/STS detectors, the sizes of its rectangular part should be at least 1.2 x 1.2 m ;

• the magnetic yoke size along the beam is equal to 1 m;• the integral of the magnetic field in the region of the

yoke of the magnet along the beam from 1 to 1.2 T*m;• the magnetic field distribution, which is similar to the

map “FieldMuonMagnet”, that is the current standard for the magnetic field for CBM simulations.

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Technical drawing

1. Beam; 2. Rack; 3. Coil; 4. Adapter; 5. Filler; 6. Support of a magnet; 7. Magnetic screens.

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The conceptual project of a magnet

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Yoke of the magnet

• Yoke material: magnetically soft steel with the low content of carbon

• Yoke sizes: 280 (310) x 260 x 100 [cm]

2.8 m

1.4 m 1.2 m2.6

0.33 m

1m

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Windings («the Cossack saddle»)

The top part of a winding with cryostat

Coil Nitric screen

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Cryostat

Top part of cryostat (front view)

Top & bottom cryostats with connectors (back view)

1.216 m

0.328 m

two adapters: - current connection;- elements of monitoring systems;- transportation of helium and nitric.

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SC winding cross-section

Vacuum casing

4.5˚K< 80˚K 300˚K

Nitric screen

Helium vessel SC cable

Cover of a vacuum casing

Helium pipe

Support of the nitric screen

Hatches

Pipe of the nitric screen(circulating liquid nitrogen) 328 mm

143.

8 m

m

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General view of the magnet

Filler facility: - evacuation of energy;- inputs for submission of liquid helium and liquid nitrogen.

Elena.Litvinenko CBM Collaboration Meeting Dubna 17 Oct 2008 10

Magnet geometry implementation for TOSCA

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Comparison with “MuonMagnet”

Used in CBM: “MuonMagnet” New design: “Muon4”

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Blue – FieldMuonMagnetRed - FieldMuon4

|By| (z) x=y=0 (target: z=0 cm)

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|B| (z,y) x=0 (target: z=0 cm)

Vertical plane along the beam:

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|By| (z,y) x=0 (target: z=0 cm)

Vertical plane along the beam:

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|B| (x,y) z=0 (target position)

z=0

Vertical plane perpendicular to the beam:

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|By| (x,y) z=0 (target position)

z=0

Vertical plane perpendicular to the beam:

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|B| (x,y) z=50 cm (magnet yoke center)

z=50

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|By| (x,y) z=50 cm (magnet yoke center)

z=50

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|By| (x,y) z=50 cm (in the limits of Station 4)

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|B| (x,y) z=100 cm (edge of the magnet yoke)

z=100

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|By| (x,y) z=100 cm (edge of the magnet yoke)

z=100

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z=160

|B| (x,y) z=160 cm (RICH entrance)

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|Bxy| (x,y) z=160 cm (RICH entrance)

|Bxy| = sqrt (Bx2+By2)

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Let us consider Standard and Compact RICH cases:

Data obtained from materials published on the site CbmRichMeeting Twiki

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z=180

|B| (x,y) z=180 cm (photodetector plane for Compact RICH)

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|B| z=180 cm (photodetector areas for Compact RICH)

0.047 (->0.04)0.058

0.042 (0.04->0.036)

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z=180

|Bxy| z=180 cm (photodetector plane for Compact RICH)

|Bxy| = sqrt (Bx2+By2)

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|Bxy| z=180 cm (photodetector areas for Compact RICH)

0.047 (->0.03)0.0494

0.028 (->0.015)

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|B| z=190 cm (photodetector plane for Standard RICH)

z=190

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|B| z=190 cm (photodetector areas for Standard RICH)

0.034 (->0.03)0.068 (->0.03)

0.034(->0.029)

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|Bxy| z=190 cm (photodetector plane for Standard RICH)

0.038 (->0.03)

0.033

0.023 (->0.02)

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Geometry implementation for Geant (cbmroot)

Yoke+Coils

+Nitric Screen

+Cryostat

+Magnetic Screens & Basement

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Compatibility with STS geometry

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I) The suggested engineering design of the superconductive dipole magnet for CBM provides the following characteristics:

angular acceptance is 50° for the height of the gap (1.2 m) and 60° for the longest part of the width of the gap (1.4 m), and the sizes of the rectangular part of the gap 121.6 x 120 cm should be suitable for the mounting of MVD/STS detectors;

the magnetic yoke size along the beam is equal to 1 m; the integral of the magnetic field in the region of the yoke of the

magnet along the beam is equal to 1.07 T*m when the current through the coils is set to a value 0.781 MA (in the case of “MuonMagnet” the current equal to 1.447 MA corresponds to the integral equal to 1.01 T*m);

the distribution of By component of the magnetic field along the beam axis is very close to the map “FieldMuonMagnet”;

the mean values of the the new magnetic field in the regions, in which the RICH photodetectors are to be placed, are about 300 Gs for the last calculated field map.

II) The 3D model of the magnet was developed for TOSCA. The magnetic field map was calculated and converted for cbmroot. A new C++ class was developed to support the changes in the symmetry of the field.

III) The Geant geometry of the magnet was created for cbmroot and tested together with the latest available STS geometry.

IV) The final decision about the sizes, shape and positions of the magnetic screens and the basement (and material of the basement) will be made after further studies directed to the magnet optimization.

Conclusion and outlook

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Backup slides

…

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|B| (x,y) z=154 cm (end of the magnetic screens)

z=154

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|By| (x,y) z=154 cm (end of the magnetic screens)

z=154

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|Bxy| (x,y) z=154 cm (end of the magnetic screens)

|Bxy| = sqrt (Bx2+By2)

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|B| and |By| (z,y) in linear scale

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“No magnetic screen” vs “Screen” cases