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Renzo_Parodi_The Panda Solenoid

VIEWS: 3 PAGES: 24

									 The Panda Solenoid
A Split Solenoid as a possible
    solution to house the
     Cluster Jet Target

           Renzo F.Parodi
Let me remind the Solenoid
parameters
• The Solenoid for the barrel spectrometer
           2T central field
           1.8 m Bore (1.6m clear bore)
           2.5 m Length
• Plus the Return Yoke
           ~3 m Diameter
           ~3.75 m Length
Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   2
   Rough solid model
• Cut view of the Iron
  Return Yoke and the
  solenoid
• The 8 fold approximation
  of the pole tips gives
  some field distortion as
  Bφ.
• A better field quality
  (more      expensive)  is
  obtained using Circular
  Pole tips.


   Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   3
                       The Panda solenoid
                        (without compensation)




Mag Field |B| on YZ Plane
Vienna, 28 july 2003        Renzo F Parodi, INFN Genoa.   4
                       The Panda solenoid
                        (without compensation)




Mag Field B on XY Plane
Vienna, 28 july 2003        Renzo F Parodi, INFN Genoa.   5
Input pending:
• Field Quality Of the solenoid needed by the
  detector(s)
• Is the Field Modulus homogeneity relevant?
• Or are the Transverse field Br (and Bφ)
  components?? (ExB effect on the drift of
  electrons in long channels)


Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   6
How to Improve field quality?
• The current in the solenoid winding can be
  graded, adding some Ampere/Turn at the
  end of the coil
• This will result (if properly done) in an
  extension of the B-modulus uniformity
• And reduction of the Br components.
• The Bφ components depend on the
  departure from the Cylindrical geometry.

Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   7
How to Improve field quality?
(Continued)


Price to pay for the field quality improvement:
The change of the conductor size along the magnet
  means
• Higher costs, either for conductor production and
  tooling for the winding.
• Different stability of different parts of the
  superconducting coil, due to a different cable
  stabilization. (This latter problem asks for a careful
  study of the magnet operation and quench)

Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   8
Coil parameters (uniform current)
• Stored energy 11 MJ
• Assuming a comfortable operation current 3-(5)
  KA we get an inductance L=2.5-(.9) H
• Assuming a discharge voltage on the Dump
  Resistor of 500V maximum (safety and Ground
  insulation reasons), the dump resistor ranges
  between 0.16 to 0.1 Ω.
• The coil dump time constant, in case of quench, is
  in the range 20 to 10 seconds (depending on the
  current choice) allowing to dump the largest part
  of the magnet energy on the external load.

Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   9
 Cryogenic Budget for the magnet
Heat Load on the Coil (4.5 K circuit) (Safety factor 2)
• radiation load on the coil~2W (60K shields 10 layers
  superinsulation)
• Conduction load (coil supports) ~1W (60K intercept).
• Gas load ~2 W P~5x10-6 mbar
• Diagnostic wires 1W
• Eddy current losses when charging (discharging)
  limited to 10 Watt (requirement) means ramp rate of
  1.7A/s or 2000-3000 s charge Time

 Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   10
 Cryogenic Budget for the magnet
Heat Load on the Shield (60 K circuit) (Safety factor 2)
• radiation load on the thermal shield ~50W (300 K 20
  layers superinsulation)
• Conduction load supports ~15W (60K intercept).
• Gas load ~2 W @ P~5x10-6 mbar
• Eddy current losses when charging (discharging)
  limited to 10 Watt @ ramp rate of 1.7A/s or 2000-
  3000 s charge Time

 Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   11
 Cryogenic Budget for the magnet
Current Leads Consumption (safety factor 1.5)
 Commercially available, optimised current
 leads (AMI) need 14 l/h LHe @ full current
 5000 A.
 Not so optimised (but safer) current leads
 require ~17 l/h LHe


 Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   12
How to insert the inner target??
• The shown solution for the solenoid is
  reasonable and feasible but….
• The cluster-jet target is not included
• We need to find room enough to allow the
  target to go trough the whole system.
• This is quite feasible for the iron Yoke (to
  some extent)
• More complex for the coil.
Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   13
Split Coil Trial Design
• Same Solenoid layout as the previous, only
  we use Two Coil with 30 cm gap Between
  the winding.
• Be careful a 30 cm Gap does not means a
  30 cm Clear Bore.
• Some spare space is already needed for
  thermal shielding and mechanical supports.

Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   14
Coil comparison




   Single Coil                                   Split Coil
Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.            15
The Panda Split solenoid




Mag Field |B| on XY Plane
Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   16
The Panda Split solenoid




Mag Field B on XY Plane
Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   17
Cryogenics

• The only difference comes from the extra load at the
  Target penetration trough the Coil_Cryostat
  complex.
• On the Cryogenic design no substantial differences
  on the Gross values of Cryogenic losses are found.
• Also the Quench behaviour of the Split Coils is
  quite the same of the single coil, provided that the
  two parts are fed in series (as is Highly
  recommended)
Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   18
  It Is this solution Good Enough?
• Can the Cluster-Jet Target Ring complex work with
  a distance of ~3 Metres between the source and the
  pumping system ??? (vacuum degradation in the
  storage Ring)
• 30 cm are enough to accommodate the needs
  (conductance) for the pumping system?
• It is the field quality of the split coil adequate for a
  smooth and reliable operation of the detectors ?
• The obtained field quality can guarantee a simple
  enough event reconstruction and data analysis?
• How much Radiation Transparent the coil must be?
 Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.    19
Sure something can be done, but not so much,
  to improve the field quality (as for the
  single coil) at the price of:

• Loss of some Stability Margin for the
  magnet operation
• Increased design complexity for coils and
  cables
• Increased overall cost for the magnetic
  system.

Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   20
I Think (and I will be happy to be wrong)
  nothing can be done (with this kind of
  magnet design) if the room available for the
  Target results not adequate.
In this case the only possibility is to proceed
  toward a different magnetic layout for the
  Barrel detector.
At the price of losses in the region covered by
  the detector. You substantially loose the
  region where the Target and ancillaries are
  placed.
Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   21
         Last Question:
  Can The Delphi magnet be used
           In Panda ?




Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   22
I see some Technical problems:
1. As Far as the field Homogeneity is concerned, when
   the end cap are removed, I think the field distribution
   will be not far enough from the field of an Air Coil,
   the iron in this case acts only as a field clamp for the
   stray field.
2. In this situation operation of the magnet without the
   end caps is impossible, at the nominal Field at least,
   due to the compression forces (axial) produced by the
   Br component at the coil end.
3. The Delphi magnet is roughly 3 times the actual size
   of the Panda Barrel; if the operation of the target is
   found marginal in the Standard design, it will be
   impossible in Delphi. Or, in alternative, you have to
                        the F Parodi, INFN Genoa.
   house and operate Renzo target inside the magnet.
   Vienna, 28 july 2003                                 23
Coming Now to the Financial point of view:

in the past Trade off considerations between

the cost benefit of using an existing magnet moved to
   a new location (including the refitting of some
   parts)
the changes and reduction in performances of the
   detector and the accelerator
the uncertainties in the available life of a Magnet,
   “Vintage late ’80”

Strongly suggested the construction of a Brand New
   magnet, at least in the case of BaBar at PepII
Vienna, 28 july 2003   Renzo F Parodi, INFN Genoa.   24

								
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