11/7/2003@KEK

Heat load for a beam loss
on the superconducting magnet

Yosuke Iwamoto, Toru Ogitsu, Nobuhiro Kimura, Hirokatsu Ohhata,
Tatsushi Nakamoto and Akira Yamamoto
Cryogenics Science Center, Applied Research Laboratory, KEKAtsuko Ichikawa
The 3rd Physics Division, Inst. for Particle and Nuclear Studies, KEKKenji Tanabe
Department of Physics, The University of Tokyo1

Introduction“Quenching” occurs when any part of a magnet goesfrom the superconducting to the normal resistive state.
SuperconductingcoilStrong beam

Normal zone
arised from heat load.

Investigate the quench stability of the superconducting cables
In case of 50GeV-10W/point beam loss
(in view of radiation shielding and maintenance)
Heat load on the cable was calculated using MARS code.
Using calculated heat load……

Measurementsof temperature rise of the cable

Quench stability simulation2

Calculation of heat load on the coil–for a 10 W/point loss by using MARS code.
coil
Iron yoke collar
Plastic spacer
YX
0 Z

Corrector

50GeV-10W beamCoil

330 cm0X

Beam tube

55 cm

Heat load on the coilSet-up in MARSHeat load will be up to 20 kJ/m3/pulse.
Heating of 0-40 kJ/m3/pulse was used in measurement and thequench simulation.
3Measurement of temperature rise of the cable
It is difficult to make an experiment using actual beam.
The cable was heated with a pulse generator.
The cable was used the same structure of LHC superconducting magnet.

current

3.6 s
10 ms

Heat load (kJ/m3/pulse) 8, 14, 20, 28, 37
Current (A)30, 40, 50, 60, 704

The cable that is used for the coil of the LHC magnets will be usedfor the J-PARC coil.
CoilThe LHC insertion region quadrupole,
MQXA magnet

Cross section of the MQXA magnet.
The NbTi/Cu strand wires are used.

Cross section of the cable using this work .
The CuNi strand wires were used in order to generate Joule heating.
5However, This cable is same structure of the coil stack for the MQXA magnet.

Cross section of the cableSpecimen
It was installed in supercritical helium bath.
(4.4 K, 0.3 MPa)

Overview
It was installed in cryostat.
6

Experimental result

28 kJ/m3/pulse heat load.
0.46 K temperature rise.

Temp. rise is proportional to heat load.

20 kJ/m3/pulse (for a 50GeV-10W beam loss)
Instantaneous temp. rise = 0.25 K
7Quench Stability Simulation
Heat balance equation
dTdT d A  k (T )
 − Pqs + gA = AC p (T )dtdx dx 

A: the overall cross section
K(T): thermal conductivity of conductor
P: strand’s wetted perimeter
qs: heat transfer to SHe
g: Joule heating in conductor
Cp(T): volumetric specific heat of conductor

heat transfer to He region
Longitudinalheat transferQuench!

Ohmic heat

Quench tends to be influenced on parameter, p/πa.
p/πa indicates the contact ratio with He and conductor.
Heliumconductor
Cross section of the cable.

No quench

Simulation result of temp. versus time.
820kJ/m3 heat load into conductor

P/πa ~ 0.4 (the actual cable)
20 kJ/m3/pulse heat load is OK(for a 50GeV-10W beam loss)

Stability margin.

120 kJ/m3/pulse heat load(for a 50GeV-60W beam loss)
may be acceptable.

MQE is minimum quench energy.
p/πa is the contact ratio with He and conductor.
9SummaryHeat load on the coil will be up to 20 kJ/m3/pulse
for a 10W/point beam loss by MARS code.

Experimental result

Quench simulation result

Instantaneous temp. risein the cable = 0.25 K

Not induce a quench.
At least,
120 kJ/m3/pulse heat load
for a 50GeV-60W beam loss
may be acceptable.

10