Helical magnets are required in RHIC and in the AGS to control proton
spin in a program for polarized proton colliding beam experiments. For RHIC, the basic construction unit is a superconducting dipole magnet
producing a four tesla dipole field that rotates through 360 degrees in
a length of 2.4 meters. The magnets are built by placing small diameter
superconducting cable into helical slots milled into thick-walled
aluminum cylinders. An iron yoke is placed around two of these nested
coils to form a single magnet. A cylindrical shell is welded around
four of these magnets and placed into a cryostat to make a Snake or a
Rotator. The particular field that is powered in each magnet, its
angular orientation and its helicity determine whether the unit will act
as a Snake or a Rotator in the RHIC lattice. Two Snakes control
the proton spin in the lattice of each ring and four Rotators in each
ring orient spin at two collision points. A collaboration with the
Japanese institute RIKEN provided partial financial support to carry out
the program.
Cross section drawing of a helical magnet
for RHIC. The inner coil diameter is 80 mm.
Photograph of a section cut from a
prototype RHIC helical dipole magnet.
For controlling proton spin in the AGS, a
single three tesla helical snake magnet is being designed and built.
This magnet will have a coil inner diameter of 200 mm and a length of
2.3 m, with two distinct pitches for the windings. Careful balancing of
the lengths and total rotation angle of each helical pitch is required
to avoid undue perturbation of the AGS beam. Various correction
windings are being planned for the magnet, to be placed on the outer
surface of the inner cold bore tube. Since the AGS tunnel does not have
cryogenic services, it is planned to cool the Snake with dewars of
liquid nitrogen and liquid helium followed by steady state cooling using
cryocoolers.
Drawing of the two-layer coils for the
AGS Snake. Note that the pitch of the helix for the center portion
of the coils is less than for the outer portion of the coils.
References:
E. Willen, R. Gupta, A. Jain, E. Kelly, G. Morgan,
J. Muratore, R. Thomas,
A Helical Magnet Design for RHIC
, PAC97, Vancouver, BC, p. 3362, May, 1997 and BNL-69117
M. Syphers, E. Courant, W. Fischer, A. Luccio, F.
Mariam, S. Peggs, F. Pilat, T. Roser, S. Tepikian, N. Tsoupas, E. Willen,
T. Katayama, T. Kawaguchi, M. Okamura, T. Tominaka, H. Wu, V. Ptitsin,
Y. Shatunov, Helical Dipole Magnets for Polarized Protons in RHIC, ibid,
p. 3359
Design Manual: Polarized Proton Collider at RHIC,
M. Syphers, Editor, BNL, July, 1998
M. Okamura, T. Tominaka, T. Kawaguchi, A. Jain, R.
Thomas, E. Willen, Field Calculations and Measurements of a Helical
Snake Magnet for RHIC, MT15, Beijing, October, 1997
T. Katayama, T. Kawaguchi, M. Okamura, T. Tominaka,
A. Jain, G. Morgan, J. Muratore, R. Thomas, E. Willen, Field Calculation
and Measurement of a Full-Length Snake Magnet for RHIC, EPAC, Stockholm,
June, 1998
E. Willen, E. Kelly, M. Anerella, J. Escallier, G.
Ganetis, A. Ghosh, A. Jain, A. Marone, G. Morgan, J. Muratore, A.
Prodell, P. Wanderer, Construction of Helical Magnets for RHIC, PAC99,
New York, March/April, 1999
W. MacKay, M. Anerella, E. Courant, J. Escallier,
W. Fischer, G. Ganetis, A. Ghosh, R. Gupta, A. Jain, E. Kelly, A. Marone,
G. Morgan, J. Muratore, M. Okamura, V. Ptitsin, A. Prodell, T. Roser, S.
Tepikian, M. Syphers, P. Wanderer E. Willen,
Superconducting Helical Snake Magnets: Construction and Measurements
, Proc. Workshop on Polarized Protons at High Energies, Hamburg, May,
1999 and BNL Spin Note 80, August, 1999
E. Willen, M. Anerella, J. Escallier, G. Ganetis,
A. Ghosh, A. Jain, E. Kelly, G. Morgan, J. Muratore, A. Prodell, P.
Wanderer, Performance of Helical Magnets for RHIC, MT16, Ponte Vedra,
FL, September/October 1999
A. Jain, Measurement of Integral Field of Helical
Dipoles, Proc. 11th International Magnet Measurement Workshop, BNL,
September, 1999
M. Okamura, T. Tominaka, T. Kawaguchi, T. Katayama,
A. Jain, J. Muratore, G. Morgan, E. Willen, Half-length Model of a
Siberian Snake for RHIC, NIM A 452(2000) 53-60
A. Jain, G. Ganetis, W. Louie, A. Marone, J,
Muratore, R. Thomas, P. Wanderer, E. Willen, Measurements of Field
Quality in Helical Dipoles for RHIC, Proc. 12th International Magnet
Measurement Workshop, October, 2002
M. Okamura, T. Katayama, T. Tominaka, T. Ohkawa, R.
Gupta, A. Luccio, W. MacKay, T. Roser, E. Willen, Design Study of a
Partial Snake for the AGS, EPAC2002, Paris, June, 2002
M. Anerella, R. Gupta,
P. Kovach, A. Marone, S. Plate, K. Power, J. Schmalzle, E. Willen,
Engineering
of the AGS Snake Coil Assembly, BNL, May 2003
E. Willen, M. Anerella,
J. Escallier, G. Ganetis, A. Ghosh, R. Gupta, M. Harrison, A. Jain, W.
MacKay, A. Marone, J. Muratore, S. Plate, R. Thomas, P. Wanderer, K.C.
Wu,
Performance Summary of the Helical Magnets for RHIC, BNL, June, 2003
R. Gupta, A. Luccio,
G. Morgan, W. MacKay, K. Power, T. Roser, E. Willen,
Magnetic Design of a Superconducting AGS Snake, BNL, June, 2003
M. Anerella, R. Gupta,
P. Kovach, A. Marone, S. Plate, K. Power, J. Schmalzle, E. Willen,
Engineering of the AGS Snake Coil Assembly,
BNL, July, 2003
For more information contact
Erich Willen
