Meeting of the Magnet Group, Sept. 2008, GSI
- Lars Schmidt: "Considerations on the Magnet Design"
- Evgeny Koshurnikov: "Status of the PANDA solenoid coil design"
- Andrea Bersani: "The PANDA Solenoid Magnet Options: a Comparison"
- Renzo Parodi: "For Discussion"
Please let me know if I forgot someone! IntiLehmann
Lars gave a brief glimpse on what he will be saying during the
technical board on Tuesday. He strongly recommended to work together,
suggesting to split the tasks into work packages.
Evgeny showed the new solenoid design from Dubna. The missing space in
the downstream region has been accounted for, balancing the force to
10t by increasing the upstream length. This would mean that the Barrel
DIRC needs to get 15cm longer. The new design includes a complete
redesign of the coil in accordance with the recommendations of the
reviewers. His concern on the coil design are shear stresses and
tension arising from the fact that the radial force on the coil former
is inhomogeneous due to the splitting of the coil in 3 parts. He
believes that a flexible spacer between the coils is needed to reduce
those forces. Also he believes that a reinforced cable would be
needed as the cable may exceed the plastic limit. Renzo argues that
the cable would only deform during the first ramping and this is how
other similar magnets are constructed.
Andrea showed an overview of the Genoa status. He stressed that the
design emphasis was on the field and detector, while the net force has
not be considered as important. He showed a new yoke design, which
includes a new DIRC readout. It is now fast and easy to change the
parameters and check new geometries. They are using 2 different
cables for the 3 coils. The cryogenic system, the temperature
distributions, and forces have been studied. Only minor modifications
were done as a reaction to the review, namely the reduction of the
ratio cold-mass to stored energy to about 5MJ/kg and a slight
reduction of the net force. The option of stabilised Al cable was
studied but price and advantages of it are not clear. Andrea showed a
comparison of the Genoa and Dubna version 1 concluding that there are
only minor differences. He ended with an moving "Epilogo" saying that
this is now really the time to join forces and work together.
Renzo showed two more symmetric yoke designs proposed by Jost (who
could unfortunately not be there). There is a long version (with
originally proposed space for the downstream endcap) and a short
version where the downstream space to the yoke is reduced by about
10cm. In the long and short versions the net force on the coil is
only 28 and 10t, respectively. Unfortunately, the field quality is
not meeting the required values by far. One might be able to improve
that a bit by optimisation, but one observes that the shorter version
is significantly worse than the longer one. His conclusion is that
keeping the field requirements one needs to either increase the
upstream end of the yoke (as in the Dubna design) or to live with a
higher net force.
Both groups agree that they prefer to leave the downstream distance
between the cryostat and yoke as it is (e.g. in v 0.1.8). The field
quality is likely to become worse when one makes the yoke shorter, but
this has not been studied in detail yet. At least there is no request
from the Magnet Group to shorten the downstream length.
-- Created by IntiLehmann
- 18 Sep 2007