Ranko Ostojic

AT/MEL

1. Beam heat loads

2. Magnet design issues related to heat loads

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 2

0.1

1

10

100

LHC experimental insertions

Dispersion suppressor Matching section Separation dipoles

Final focus

P/L (W/m)pp collisions at 7 TeV generate 900 W at Lnom

carried by the secondaries to each side of LHC experimental insertion.

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 3

Heat load in the Low- Triplet

Average load: 7 W/mPeak: 14 W/mTotal: 205 W

Total integrated heat load to inner triplet = 205.5 Watts

<---Q1 quad---> <----Q3 quad----> <--------------Q2 quad--------------->

Heat Load in Inner Triplet Quads versus Position

0

2

4

6

8

10

12

14

16

Heat "bin" (blue are 0.55 m long, red about 1 m long)

He

at

to 1

.9 K

(W

/m)

T. Peterson, FNAL Technical Note July 2002

External Heat Exchanger

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 4

Heat load in the Low- Triplet

N. Mokhov et al, LHC Project Report 633Peak power density:

0.45 mW/g

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 5

MQXA low- quadrupole (KEK)

Coil ID 70 mmG = 215 T/m at 1.9 K

Conductors 1/2 Width 11/11 mm Mid-thick 1.48/1.34 mm Strand dia 0.815/0.735 mm No strands 27/30

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 6

MQXA Heat Transfer Experiments (I)

Exp ConductorStrand material Cu-NiStrand dia 0.814 mmNo strands 27Cross-section 1.47 x 11 mmLength 177 mm

InsulationUpilex 15 mm/25 mpitch 50% overlap

+Upilex 6 mm/50 mB-stage epoxy 10 mpitch 8 mm (2 mm

gap)

N. Kimura et al, IEEE Trans. Appl. Superconductivity, Vol 9, No 2, (1999) p 1097.

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 7

MQXA Heat Transfer Experiments (II)

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 8

MQXA Heat Transfer Experiments (III)

Conclusions:-effective channel diameter ~ 35 m-Conduction important at higher heat flux-AC loss measurements give consistent results-Maximum allowed heat load ~ 18 mW/cm3

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 9

MQXB low- quadrupole (FNAL)

Coil ID 70 mmG = 215 T/m at 1.9 K

Conductors 1/2 Width 15.4/15.4 mm Mid-thick 1.45/1.14 mm Strand dia 0.808/0.650 mm No strands 37/46

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 10

MQXB Heat Transfer Experiments (I)

Insulation1st coil layer

Polyimide 9.5 mm/25 mpitch 55% overlap

+Polyimide 9.5 mm/50 mQXIpitch 11.5 (2 mm

gap)

2nd coil layerPolyimide 9.5 mm/25 mpitch 43% overlapPolyimide 9.5 mm/25 mQXIpitch 50% overlap

L. Chiesa et al, IEEE Trans. Appl. Superconductivity, Vol 11, No 1, (2001) p 1625.

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 11

MQXB Heat Transfer Experiments (II)

Conclusions:-AC loss results consistent with assumption of “blocked cooling channels”-Maximum allowed heat load ~ 1.6 mW/g

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 12

MQM matching quadrupole

Coil ID 56 mmGradient 200 T/m at 1.9 K

160 T/m at 4.5 K

ConductorWidth 8.8 mmStrand dia 0.480 mmNo strands 36

InsulationPolyimide 8 mm/25 mpitch 50% overlap

+Polyimide 9 mm/50 munc. poly. 6 mpitch 11 mm (2 mm

gap)

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 13

MQY wide aperture quadrupole

Coil ID 70 mmGradient 160 T/m at 4.5 K

Conductor 1/2Width 8.3 mmStrand dia 0.48/0.73 mmNo strands 34/22

InsulationPolyimide 8 mm/25 mpitch 50% overlap

+Polyimide 9 mm/50 munc. poly. 7 mpitch 11 mm (2 mm

gap)

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 14

Separation dipoles (BNL)

Coil ID 80 mmField 3.8 T at 4.5 K

(2.4 T at 4.5 K in IR1/5)

ConductorWidth 9.73 mmStrand dia 0.648 mmNo strands 30

InsulationKapton CI 9 mm wide

50 m thickpitch 50% overlap

+Kapton CI 9 mm

50 mpitch 50% overlap

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 15

MQTL

Coil ID 56 mmGradient 120 T/m at 1.9 K

90 T/m at 4.5 K

SC wire 0.73 mm x 1.25 mm (with enamel insulation)

Coil Insulationepoxy impregnated

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 16

Heat transfer in Saturated He Bath

Y. Iwamoto et al, IEEE Trans. Appl. Superconductivity, Vol 14, No 2, (2004) p 592.

Quench Stability Study of J-PARC Magnets

Cable and insulation identical to MQXA

20 mJ/cm3 in a 10 ms pulse

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 17

Summary of expected quench limits

Magnet Coil insulationOperating

temperatureConditions/Reference

Temperature margin

Heat reserve (transient losses)

Peak power density

Temperature margin

Heat reserve (transient losses)

Peak power density

MB 2x50mu (50% overlap) + 73 mu (2 mm gap) 1.9 K 7 K 38 mJ/cm3 10 mW/cm3 1 K 0.8 mJ/cm3 5 mW/cm3 LPR 44; Meuris et al. (1999)MQXA 2x25mu (50% overlap) + 60 mu (2 mm gap) 1.9 K 8.2 K 55 mJ/cm3 1.3 K 1.3 mJ/cm3 4 mW/cm3 Kimura et al, IEEE Tran SC., 9(1999)1097MQXB 2x25mu (55% overlap) + 50 mu (2 mm gap) 1.9 K 8 K 50 mJ/cm3 1.2 K 1.2 mJ/cm3 0.4 mW/g Mohkov et al., LPR 633MQM 2x25mu (50% overlap) + 55 mu (2 mm gap) 1.9 K 7.5 K 50 mJ/cm3 10 mW/cm3 1 K 1.0 mJ/cm3 5 mW/cm3MQM 2x25mu (50% overlap) + 55 mu (2 mm gap) 4.5 K 6.5 K 75 mJ/cm3 1.2 K 5 mJ/cm3 2 mW/cm3MQY 2x25mu (50% overlap) +55 mu (2 mm gap) 4.5 K 6.5 K 75 mJ/cm3 1.4 K 5 mJ/cm3 2 mW/cm3MQTL B-stage epoxy impregnated 4.5 K 6.5 K 75 mJ/cm3 2 K 5 mJ/cm3 1.0 mW/cm3 R.Wolf, Pr comm., 28 July 2004

Injection Collision

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 18

Possible experiments on production magnets

QH L4

QH L2-3

MQY in B4:-Use one QH L2-3 for coil heating -Magnet protection by QHL4

MQM and MQY in SM18:-Use anti-cryostat heaters to verify operating margins at 4.5 K

Insertion Magnets and Beam Heat Loads

R. Ostojic, AT/MEL 19

Conclusions

• Heat loads associated to pp collisions are considerable in the experimental insertions, in particular in the low-beta triplets.

• Thermal properties of the coils of both types of low-beta quadrupoles were experimentally studied, and confirm a safety factor of 3 with respect to expected heat load for nominal luminosity.

• MQM and MQY quadrupoles have insulation schemes analogous to the MB. Similar thermal properties could be expected, but have not been experimentally verified.

• Magnets operating at 4.5 K are expected to have higher quench limits for transient losses, but lower for continuous losses than at 1.9K.