ENERGY DEPOSITION IN HYBRID

NbTi/Nb3Sn TRIPLET CONFIGURATIONS

OF THE LHC PHASE I UPGRADE

Fermilab Accelerator Physics Center

Nikolai Mokhov, Fermilab

CERNMarch 31 – April 2, 2008

JIRS meetings, CERN, Mar. 31 – Apr. 2, 2008 Energy Deposition in Hybrid IR Phase I Upgrade - N. Mokhov2

OUTLINE

•Introduction

•Three Upgrade Configurations Studied

•MARS15 IR and Quad Models

•Power Density Maps

•Peaks w.r.t. Design Limits

•Heat Loads

•Summary

JIRS meetings, CERN, Mar. 31 – Apr. 2, 2008 Energy Deposition in Hybrid IR Phase I Upgrade - N. Mokhov3

INTRODUCTION

JIRS project of the LARP aims at investigation of potential of replacing one (on each side of IP) of the NbTi quadrupoles with a Nb3Sn one in the LHC Phase I upgrade of high-luminosity IRs. Based on realistic energy deposition calculations, we are trying to derive operational margins for the quads in various configurations. Preliminary results are presented here.

Simulations are done with MARS15 (2008), and DPMJET-3 as an event generator for 7x7 TeV pp-collisions at 2.5x1034 cm-2 s-1, using low-betamax and symmetric optics from John Johnstone.

IP5 (R) is considered, with a full crossing angle of 450 rad, segmented absorbers SS or W (possibly) cooled at LN2-temperature, as proposed in our paper PRSTAB, 9, 10001 (2006) and Proc. WAMDO06 Workshop, CARE-Conf-06-049-HHH, p. 80 (2006).

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1. LOW-BETAMAX OPTICS: LBM-1 in MARS15

Q1: 90-mm NbTi, 167.2 T/m, L=7.06 m

Q2: 130-mm NbTi, 121.4 T/m, L=7.787m x 2

Q3: 110-mm Nb3Sn, 176.2 T/m, L=3m x 2

TAS aperture:(a) 42 mm(b) 55 mm3-mm segment

absorbers:W in Q1, SS in Q2, no in Q3

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2. LOW-BETAMAX OPTICS: LBM-2 in MARS15

Q1: 90-mm Nb3Sn, 206.1 T/m, L=5.65 m

Q2: 130-mm NbTi, 121.1 T/m, L=7.787m x 2

Q3: 130-mm NbTi, 121.1 T/m, L=8.711 m

TAS aperture: 55 mm3-mm segment

absorbers:SS in Q1, Q2 & Q3

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3. SYMMETRIC OPTICS: SYM-1 in MARS15

Q1: 90-mm Nb3Sn, 203.8 T/m, L=2.75m x 2

Q2: 130-mm NbTi, 121.9 T/m, L=7.8m x 2

Q3: 130-mm NbTi, 121.9 T/m, L=9.2 m

TAS aperture: 55 mm3-mm segment

absorbers:SS in Q1, Q2 & Q3

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90, 110 and 130-mm Quad Design

OPERA-calculated 2-D magnetic maps:200, 180 and 125 T/m, x = y = 2 mm

By Vadim Kashikhin

90-mm

110-mm

130-mm

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MARS15 IMPLEMENTATION

90-mm Nb3Sn 130-mm NbTi

Same scale

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Beam screens, segment absorbers, cold bore, kapton,LHE, coils, collar, yoke and cryostat in MARS15

Same scale90-mm Nb3Sn 130-mm NbTi

Cryostat: thermal shield and vessel (R=457 mm)

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CONSISTENCY CHECKS

Example: LBM-2

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Particle Tracks for 1 pp-event at 7x7 TeV

Example: SYM-1

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POWER DENSITY MAP: LBM-1

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Power Density Profiles at Longitudinal Peaks: LBM-1

Quad endsQ1 non-IP

Q2b non-IP

Q3a IP

Q3b IP

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POWER DENSITY MAP: LBM-2

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POWER DENSITY MAP: SYM-1

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Power Density Profiles at Longitudinal Peaks: SYM-1

Q1b non-IP end Q2b non-IP end

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QUENCH LIMITS & DESIGN GOAL

Quench Limit

mW/g mW/cm3 mW/g mW/cm3

NbTi 1.6 11.2 0.53 3.71

Nb3Sn 5 34 1.66 11.3

Design Goal

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Low-betamax-1: Peak Power Density in Cable-1 vs z

LBM-1: 42-mm TAS LBM-1: 55-mm TAS

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LBM-2 & SYM-1: Peak Power Density in Cable-1 vs z

LBM-2 SYM-155-mm aperture TAS

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Peak Power Density wrt Design Limits

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HEAT LOADS

At L=2.5x1034 cm-2 s-1, pp-interactions result in power of 2.24 kW per beam carried out from IP1 and IP5. About 1/3 of this power is deposited in the TAS and triplet.

Power dissipation in the TAS scales with the luminosity and decreases with aperture increase thus giving rise to the power deposited in cold components.

TAS: 455W at 34mm, 360W at 42mm, and 283W at 55mm.

Heat loads in low-betamax (LBM-2) optics (Watts):

109 (Q1), 20 (MCBX), 74 (Q2a), 84 (Q2b), 25 (MQSX), 7 (TASB), 80 (Q3), 11 (MCBXA), 27 (DFBX), 17 (vessel).

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HEAT LOAD BALANCE (Watts)

LBM-1 LBM-2 SYM-1

LHe (bore, SC, collar, yoke)

264 306 292

“LN2” (beam screen and segm. absorber)

173 101 104

Room T (vessel) 20 20 23

Total 457 427 419

Grand total(TAS included)

740 710 702

55-mm TAS Q1 to MCBXA ~ 40 m

~6.6 W/m

LHe+”LN2” ~11 W/m

~7.7 W/m

LHe+”LN2” ~10 W/m

~7.3 W/m

LHe+”LN2” ~9.9 W/m

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SUMMARY (1)

1. There are always four pronounced peaks in

longitudinal distributions of maximum power density in the first SC cable (averaged over the cable area at the azimuthal maxima): close to Q1 non-IP end, Q2a IP end, Q2b non-IP end and Q3 IP end (see also LHC PR 633, 2003).

2. For the configurations considered all the peaks are safely below the design limits (for 55-mm TAS).

3. Increasing TAS aperture from 42 to 55mm, increases first peak by 10% and heat load to the cold components by 75 W.

4. 3-mm tungsten absorbers in Q1 provides reduction of peaks by a factor of about 3 and 2 in Q1 and Q2, respectively, compared to the stainless steel ones.

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SUMMARY (2)

5. Peak in Q3 is practically insensitive to the

configuration.

6. Compared to the nominal case, dynamic heat loads to theSC quads are certainly higher at 2.5x1034 cm-2 s-1 and enlarged TAS aperture, but – because of larger quad apertures and use of absorbers - seem to be manageable, especially with high-Z absorbers cooled at LN2.

7. Using Nb3Sn for Q1 or Q3 instead of NbTi substantially increases operational margins, frees space for instrumentation between quads, and provides verification of this new technology for Phase II.

8. Thanks to J. Johnstone for optics, V. Kashikhin for quad geometry and magnetic field maps, I. Rakhno & S. Striganov for enhancement of analysis tools, and A. Zlobin for coordination.