This chapter is the second part in a series of publications
on the Compact Muon Solenoid (CMS) detector magnetic field map creation. The
CMS detector at the Large Hadron Collider has a heterogeneous solenoid magnet
where the created magnetic flux penetrates both nonmagnetic and ferromagnetic
materials of the experimental setup. The chapter describes the performance of
the magnetic field measuring and monitoring systems for the CMS detector. To
cross-check the magnetic flux distribution obtained with the CMS magnet model,
four systems for measuring the magnetic flux density in the detector volume
were used. The magnetic induction inside the 6 m diameter superconducting
solenoid was measured and is currently monitored by four nuclear magnetic
resonance (NMR) probes installed using special tubes at a radius of 2.9148 m
outside the barrel hadron calorimeter at ±0.006 m from the coil median
XY-plane. Two more NMR probes were installed at the faces of the tracking
system at Z-coordinates of -2.835 and +2.831 m and a radius of 0.651 m from the
solenoid axis. The field inside the superconducting solenoid was precisely
measured in 2006 in a cylindrical volume of 3.448 m in diameter and 7 m in
length using ten three-dimensional (3D) B-sensors based on the Hall effect (Hall
probes). These B-sensors were installed on each of the two propeller arms of an
automated field-mapping machine. In addition to these measurement systems, a
system for monitoring the magnetic field during the CMS detector operation has
been developed. Inside the solenoid in the horizontal plane, four 3D B-sensors
were installed at the faces of the tracking detector at distances X = ±0.959 m
and Z-coordinates of -2.899 and +2.895 m. Twelve 3D B-sensors were installed on
the surfaces of the flux-return yoke nose disks. Seventy 3D B-sensors were
installed in the air gaps of the CMS magnet yoke in 11 XY-planes of the
azimuthal sector at 270°. A specially developed flux loop technique was used
for the most complex measurements of the magnetic flux density inside the steel
blocks of the CMS magnet yoke. The flux loops are installed in 22 sections of
the flux-return yoke blocks in grooves of 30 mm wide and 12–13mm deep and
consist of 7–10 turns of 45-wire flat ribbon cable. The areas enclosed by these
coils varied from 0.3 to 1.59 m2 in the blocks of the barrel wheels and from
0.5 to 1.12 m2 in the blocks of the yoke endcap disks. Measurement of the
magnetic flux density in the steel blocks of the magnet yoke using flux loops
and three-dimensional B-sensors confirmed the correctness of the magnetic flux
distribution modelling in the muon momenta measuring system, which provided a
high muon momentum resolution and a reliable muon identification. The
development of the magnetic field measurement and monitoring systems and the
results of the magnetic flux density measurements across the CMS magnet are
presented and discussed in this chapter.
Author(s) Details:
Vyacheslav Klyukhin,
Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State
University, RU-119992 Moscow, Russia and European Organization for Nuclear
Research (CERN), CH-1211 Geneva 23, Switzerland.
Austin
Ball,
European
Organization for Nuclear Research (CERN), CH-1211 Geneva 23, Switzerland.
Felix Bergsma,
European Organization for Nuclear Research (CERN), CH-1211 Geneva
23, Switzerland.
Henk Boterenbrood,
Nikhef, 1098XG Amsterdam, The Netherlands.
Benoit Curé,
European
Organization for Nuclear Research (CERN), CH-1211 Geneva 23, Switzerland.
Domenico
Dattola,
Department
of Physics, Polytechnic University of Turin, I-10129 Turin, Italy.
Andrea Gaddi,
European Organization for Nuclear Research (CERN), CH-1211 Geneva
23, Switzerland.
Hubert Gerwig,
European Organization for Nuclear Research (CERN), CH-1211 Geneva
23, Switzerland.
Alain Hervé,
Department of Physics, University of Wisconsin, Madison, WI 53706, USA.
Richard Loveless,
Department of Physics, University of Wisconsin, Madison, WI 53706, USA.
Gary Teafoe,
FNAL, Batavia, IL 60510-0500, USA.
Daniel Wenman,
Department of Physics, University of Wisconsin, Madison, WI 53706, USA.
Wolfram Zeuner,
European Organization for Nuclear Research (CERN), CH-1211 Geneva 23,
Switzerland.
Jerry Zimmerman,
FNAL, Batavia, IL 60510-0500, USA.
Please see the link here: https://stm.bookpi.org/CPPSR-V7/article/view/13449
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