CLAS12 Magnets General Requirements

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CLAS12 Magnets General Requirements

Latifa Elouadrhiri
Conceptual Design and Safety Review of
Superconducting Magnets Jefferson Lab September
26-28, 2006
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Outline

• Brief Description of the CLAS Detector
• Motivation for the CLAS12 Upgrade
• Physics and Detector Design Requirement for the
  CLAS12 Magnets
• CLAS12 Detector Design Parameters
• Summary

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Hall B Overview

• Hall B currently houses the CLAS detector.
• CLAS will be modified and upgraded to CLAS12,
  which will be worldwide the only full acceptance,
  multi-purpose detector for fixed target electron
  scattering experiments.
• CLAS12 will operate with an upgraded luminosity
  of gt1035cm-2s-1, more than an order of magnitude
  increase over current luminosity.
• With these capabilities, CLAS12 will support a
  broad experimental program in fundamental nuclear
  physics.

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CEBAF Large Acceptance Spectrometer (CLAS)
Torus magnet 6 superconducting coils
Large angle calorimeters Lead/scintillator, 512
PMTs
Liquid D2 (H2)target, NH3, ND3 g start counter
e- minitorus
Gas Cherenkov counters e/p separation, 216 PMTs
Drift chambers argon/CO2 gas, 35,000 cells
Electromagnetic calorimeters Lead/scintillator,
1296 PMTs
Time-of-flight counters plastic scintillators,
684 PMTs
Operating luminosity 1034cm-2s-1
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CLAS Torus installation in Hall B (1995)
CLAS Torus
cross bars for out-of-plane support
protective cover
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Present-day CLAS
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CLAS Detector Perfomance
Missing mass spectrum for g p ? pX

• All design parameters have been met
• In routine operation since 1997

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CLAS12 Key Physics Programs

• Generalized Parton Distributions and
  femto-tomography of the nucleon.
• Quark orbital angular momentum contributions to
  the nucleon spin
• Spin structure functions of the nucleon in the
  valence quark domain.
• Free neutron structure function and moments in
  neutron tagging,
• Neutron magnetic form factor at highest Q2.
• Quark propagation and quark hadronization using
  the nucleus as a laboratory.
• Quark confinement in the 3-quark system through
  baryon excitations.

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CLAS12 Requirements
The 12 GeV physics program requires measurement
of exclusive reactions. At high energies cross
sections are small and high energy particles are
produced in the forward direction. The physics
program requires

• High operating luminosity of 1035 cm-2sec-1
• Small angle capabilities for charged and neutral
  particle detection
• Particle ID to higher momentum (e-/p-, p/K/p,
  g/po)
• More complete detection of hadronic final state
• Compatibility with polarized target operation

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CLAS12 Requirements and Design Solution

• Requirements
• Need high statistics capabilities for exclusive
  processes
• High operating luminosity of gt1035 cm-2sec-1
• Particle ID to higher momentum (e-/p-, p/K/p,
  g/po)
• More complete detection of hadronic final state
  

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Utilization of existing Hall B Equipment

• Re-use existing CLAS components
• Forward electromagnetic calorimeters
• Low threshold gas Cerenkov counters
• Time-of-flight scintillators
• Drift chamber electronics and gas system
• Inner PbW04 small angle calorimeter
• DAQ and readout electronics

Direct impact on CLAS12 magnet designs.

• Re-use other Hall B components
• Photon energy tagging system
• Coherent bremsstrahlung/goniometer
• Cryogenic targets
• Frozen spin polarized target
• Moller polarimeter
• Faraday cup
• Beam diagnostics
• Pair spectrometer PS
• Raster magnets PS
• Utility distribution space frames

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CLAS12 Magnets Upgrade

• The CLAS12 physics program requires magnetic
  analysis of charged particles in the polar angle
  range of 5o 40o and covering most of the
  azimuthal angle range. This is achieved by a
  superconducting Torus magnet with symmetric six
  coil geometry.
• The CLAS12 physics program requires magnetic
  analysis of charged particles in the polar angle
  range of 40o 135o and covering the entire
  azimuthal angle range. In addition, operation of
  a polarized target is required in a highly
  uniform magnetic field of up to 5 Tesla. This is
  achieved by a superconducting Solenoid magnet.

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CLAS12 - Detector
Forward Calorimeter
Preshower Calorimeter
Forward Cerenkov (LTCC)
Forward Time-of-Flight Detectors
Forward Drift Chambers
Superconducting Torus Magnet
Inner Cerenkov (HTCC)
Central Detector
Beamline Instrumentation
Inner Calorimeter
Reused detectors from CLAS
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CLAS12 Single sector (exploded view)
Beamline equipment
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CLAS12 Central Detector
(B0 5 T)
TOF light-guide
Cryostat vacuum jacket
SiliconTracker
Space for e.m. calorimeter
Main coil
Shielding coil
Central TOF
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CLAS12 - Design Parameters 
Forward Detector
Central Detector
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CLAS12 Torus - Requirements
CLAS12 Coil geometry

• Generate high ?Bdl, needed for good dp/p for high
  momentum forward-going charged particles.
• Retain six coil geometry to allow use of the
  existing CLAS forward detectors.
• Incorporate design attributes from the CLAS
  Torus.
• Simplify force containment and improve knowledge
  of the geometry and magnetic fields

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Solenoid Requirements
CLAS12

• Provide magnetic field for charged particle
  tracking for CLAS12 in the polar angle range from
  40o to 135o.
• Provide magnetic field for guiding Møller
  electrons away from detectors.
• Allow operation of longitudinally polarized
  target at magnetic fields of up to 5 Tesla, with
  field in-homogeneity of ?B/B lt 10-4 in cylinder
  of 5cm x 3cm.
• Provide full coverage in azimuth for tracking.
• Sufficient space for particle identification
  through time-of-flight measurements.
• Minimize the stray field at the PMTs of the
  Cerenkov Counter
• Minimize the forces created by one magnet on the
  other

CLAS12 Solenoid
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CLAS12 Magnet shielding
With solenoid field
No solenoid field
CLAS12 Solenoid provides magnetic field for
guiding Møller electrons away from detectors
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Summary

• The magnetic configuration for the CLAS12
  Detector are well defined. They were developed
  based on
• Extensive simulation of the physics processes of
  the 12 GeV science program
• Extensive detailed design and simulation of the
  CLAS12 detectors that impact the magnet design
• Optics of the High Threshold Cerenkov Counter
• Geometry of the Forward Silicon Detector
• Geometry and design of the Polarized target
• Extensive background simulations to calculate the
  rates and radiation doses on the central
  detectors (TOF and SVT) and on the forward
  detectors (SVT, HTCC, Drift Chambers) to make
  sure of the high luminosity capabilities.