cern-care workshop hhh2004, 8 november 2004 technological challenges for the lhc upgrade w. scandale...

CERN-CARE Workshop HHH2004, 8 November 2004

Technological Challenges for the LHC Upgrade

W. ScandaleCERN Accelerator Technology Department

Thanks to the valuable contributions of D. Tommasini

Walter Scandale - 8 November 2004 - HHH2004 workshop 2

Present context

A road map for the upgrade of the LHC luminosity

Technological challenges High-field superconducting magnets for the LHC-IR Medium-field fast-cycling superconducting magnets for

the LHC-injector complexSPL and RCS

Conclusive remarks

Outlook


LHC in operation within about 30 months GSI program based on SIS100 and SIS300 approved EU-CARE activities settled

HHH-network investigating Possible scenarios for LHC upgrade New concepts for Interaction Regions design Possible use of high-field and for medium-field fast-pulsed magnets

NED-Joint Research Activity (NED-JRA) launching R&D for high-field Nb3Sn superconducting wire New concepts for the design of high-field superconducting IR magnets

HIPPI-Joint Research Activity (HIPPI-JRA) launching R&D for high-intensity pulsed linear accelerators Optimization of up to 200 MeV Linac Beam dynamics and RF component design for Linac up to the GeV energy

Potential interest of CEA-Saclay, CERN, GSI and INFN to strengthen the SC magnet R&D program

US-LARP very active on high-field Nb3Sn superconducting quadrupoles (about 2 M$/year from DOE)

Present Context


A Road Map for the LHC Upgrade

Baseline hardware: ultimate performance -> Lmax~ 2.3x1034/cm2 s-1

Ultimate bunch intensity -> Ib = 1.7•1011 protons per bunch Requires RF batch compression in the PS or Linac4 Two collision points (instead of four) with = 315 rad (instead of

300)

Luminosity increase by reducing * -> Lmax~ 4.6x1034/cm2 s-1

IR quadrupole upgrade (higher aperture - higher pole field) -> *=0.25 m

larger crossing angle -> = 445 rad (Crab crossing RF-cavities?)

Beam density increase and LHC turn-around upgrade RF upgrade for bunch compression in the LHC Super-PS and super-SPS injecting at 1TeV (first step for future LHC

energy upgrade)

Beam energy increase Higher field dipoles (14 T) and higher gradient quadrupoles (500

T/m) Mass production of a new superconductor (most likely Nb3Sn)

See LHC Project Report 626


A Time-Window for LHC-IR Upgrade

Due to the high radiation doses to which they will be submitted, the life expectancy of LHC IR quadrupole magnets is estimated ~5-7 years

IR-quadrupoles will have to be replaced in 2013-2015, thereby offering an opportunity of upgrading LHC IR optics to improve luminosity

Mid-2010’s is also the earliest time frame when one can expect to need final-focusing quadrupole magnets for any of the proposed projects of linear colliders. At least one needs very strong wide final triplets

Radiation damage limit ~700 fb-1

Courtesy of F. Ruggiero and Jim Strait


IR based on High Fields Magnets with reduced *

New Interaction Regions: beam dynamics versus magnet technology and design

See PAC03 pp 42-44

blue DIPOLESred QUADRUPOLESgreen RF-CAVITIES


R&D needed for High Field Magnets

SC Cable High performance SC cable aiming at a non-Cu JC up to 1500

A/mm2 @15 T at a temperature of 4.2 K or 1.9 K

Insertion and magnet design Simultaneous optimization of optics and magnet design 15 T dipoles and 12 T - 100 mm quadrupoles of accelerator

type (reasonable quench margin and good field region, easy to build)

Particle loss hardness Upgrade of the Heat Transfer in SC cables; Comparative study among 4.2 K and 1.9 K solutions

(imposing the constraint of the LHC cryogenic plant) Upgrade simultaneously radiation hardness (cable

insulators and coil design) and local collimator layout


SC conductor for High Field Magnets

High Temperature Superconductors (HTS) are not yet ready for large-scale applications requiring high current densities under high magnetic fields. It will take at least another decade before they become competitive in terms of performances, yield and cost

The upper critical field of MgB2 is too low

Nb3Al exhibits promising properties but there are serious manufacturing issues that have yet to be resolved

At present, the only serious candidate to succeed NbTi, suitable for industrial production, is the intermetallic compound Nb3Sn (world production still rather low: ~15 t/year).

R&D on Nb3Sn conductor started in the frame of CARE-NED

See CARE-HHH-AMT workshop WAMS 22-24 March 2004 Archampshttp://amt.web.cern.ch/amt/activities/workshops/WAMS2004/WAMS2004_index.htm


High Field Magnets: recent results

A series of record-breaking dipole magnet models, opening the 10-to-15 T field range (however, not yet of accelerator class)

11 T on first quench at 4.4 K

in a 50-mm-bore (Twente University, 1995)

13.5 T at 1.8 Kin a 50-mm bore

(LBNL, 1997)

14.7 T at 4.2 K in a 25-mm gap

(LBNL, 2001)

MSUT (cos)D20

(cos)

RD-3 (Racetrack

)


The ‘poor man’ way: LHC-IR upgrade with new NbTi quadrupoles ->

*=0.25 m

The quadrupole aperture is matched to the real beam size

Comparison between NbTi,NbTiTa and Nb3Sn conductors

See EPAC 04 pp 608-10


The main objective of the NED JRA is to develop a large-aperture (more than 88 mm), high-field (up to 15 T) dipole magnet model relying on high-performance Nb3Sn conductors (non-Cu JC up to 1500 A/mm2 @15 T and 4.2 K).

Such magnet is aimed at demonstrating the feasibility of the LHC-IR upgrade scenarios based on high field dipole and quadrupole magnets and is meant to complement the US-LARP.

In addition, the NED model could be used to upgrade the CERN superconducting cable test facility (presently limited to 10-10.5 T).

The NED JRA proposal involves 7 collaborators (CEA/Saclay, CERN, INFN-Milan and Genoa, RAL, Twente University and Wroclaw University), plus several industrial sub-contractors.

EU funding limited to 25 % of the original request -> new resources needed soon to complete the program

The EU Joint Research Activity CARE-NED


De-scoping CARE-NED

Given the present State of the Art and the magnet requirements foreseen for LHC IR upgrade and for IR’s of future linear colliders, we established the following road-map:

revisit magnetic and mechanical designs to achieve enhanced performances with coils made from brittle conductors,

address coil cooling issue under high beam losses,

keep promoting high-performance Nb3Sn wire development (to ensure the survival of multiple suppliers including in EU),

improve mechanical robustness and assess radiation hardness of Nb3Sn conductor insulation,

put into practice all of the above in magnet models and prototypes.


Beam Density Increase

The upgrade of the injector chain is needed

Up to 160 MeV: LINAC 4 Up to 2.2 GeV: the SPL (or a super-BPS)

The superconducting way:

Up to 60 GeV a SC super-PSUp to 1 TeV a super SPSSC transfer lines to LHC

The normal conducting way:

Up to 30 GeV a refurbished PSUp to 450 GeV a refurbished SPS

A 1 TeV booster ring in the LHC tunnel may also be considered

Easy magnets (super-ferric technology?) Difficult to cross the experimental area (a bypass needed?)

Rich-man way:

Poor-man way: RF upgrade for batch compression in the PS

See CARE-HIPPI

See CARE-HHH and CARE-NED


Low Energy Injector Upgrade:

LINAC4 & SPL

0.9•1014 particles at 2 Hz for the PS booster

see CERN-AB-2004-21

2.3•1014 particles at 50 Hz for the PS


Upgrade of the Injector Rings:

Booster, PS and SPS Basic investigations still needed

Main constraints: Use the existing tunnels Increase the beam density and the beam intensity

possibly by a large factor Fast repetition rate to speed-up the LHC injection

process

Expected challenges Fast-cycling SC magnets Powerful RF within a limited space Cryogenic, vacuum Ejection optimization, loss control, beam disposal,

instrumentation


Recent Activity on Fast Cycling

Dipoles SIS 200 (abandonned) 4 T central field, 1 T/sec ramp Design based on RHIC dipoles Costeta, Rutherford cable One phase He cooling

BNL model : optimize to higher ramp-rate Wire twist pitch 4 mm instead of 13 mm Stabrite coating instead of no coating Stainless steel core (2x25 microns) G-11 wedges instead of copper wedges Thinner yoke laminations (0.5 mm instead of 6.35 mm), 3.5 % silicon, glued with

epoxy.

Courtesy A.Ghosh and P.Wanderer

Cable inner edge


The BNL Fast Cycling Dipole Model

Courtesy A.Ghosh

Cross section of GSI-001 Prototype Magnet


The SIS 300 Fast Cycling Dipole

Model SIS 300 6 T, 1 T/sec ramp, 100 mm

bore Design based on UNK dipoles,

bore from 80 mm to 100 mm 2-layers Cos, Rutherford cable One phase He cooling

Challenges : high operational field for 4.2 K, pulsed, high losses

Activity on cable development: Reduction of conductor AC loss adjusting filament hysteresis, strand matrix

coupling current, cable crossover resistance Rc, and adjacent resistance Ra. A 3.5 micrometer filament diameter was chosen because it appears to be the

minimum value that can be reached in a standard copper matrix strand without the onset of proximity coupling.

The use of a Cu-0.5% Mn as an interfilamentary matrix material is also under consideration, to reduce both matrix coupling current losses (due to the high resistivity of CuMn ) and hysteresis losses.

Coil

Collars

Key

Iron yoke

Shell

C-ClampStaples

Courtesy of G.Moritz


Cables for Fast Pulsed Dipoles

A.D. Kovalenko, JINR, 2004


R&D Still Needed(a non-exhaustive list)

Lowering losses in pulsed magnets Industrialize filament size 3.5 microns or smaller, reduce twist pitch Electromagnetic design for minimum amount of superconductor Optimize cable (cable size, keystone angle, number of strands) Cored cables and strands with resistive coating :

long term behaviour issues investigate limits of high Ra/Rc keeping acceptable current sharing

Resistive matrix Alternatives to Rutherford cables, such as Nuclotron and CICC

Other issues Thermal modelling of magnet cross section under helium flow Characterization of cable insulation schemes (dielectric/mechanical/thermal) Manufacture of a small scale prototype for thermal model/parameter validation,

for cable testing/characterization, and as coil test facility Manufacture of an optimized prototype to prepare series production Field quality during the ramp : modellization and experiments Develop dedicated magnetic measurement systems for fast varying magnetic

fields


Pulsed Dipoles for PS and SPS?

Initial considerations based on known technology

Upgraded PS and SPS may require two different types of pulsed magnets

3T – 2T/s for the PS

5T – 1.5 T/s for the SPS

The quench limit performance ican be achieved with present technology

Modified RHIC dipoles or Nuclotron/CICC cable based dipoles for PS

Modified (lower losses) « SIS 300 » type dipoles for the SPS


Technological Challenges

A SC dipole for the SPS may produce 70 W/m peak (35 W/m effective 140 kW for the SPS, equivalent to the cryogenic power of the LHC !)

A rather arbitrary ‘guess’ for beam loss is of about 1012px100GeV/10s= 15 kW

By dedicated R&D magnet losses should be lowered to 10 W/m peak (5 W/m effective 20 kW ), comparable to expected beam loss power

1 s

3 s

3 s 3 s

5 T

Tentative SPS cycle

Losses are a major concern -> Vigorous R&D program needed Study and evaluate different scenarios of beam losses in PS and

SPS

Study and evaluate a maximum allowed cryogenic budget

Optimize the dipoles not only for good quench performance in condition of cable/iron losses, but also for cryogenic budget


What about High Power Beams ? seeH.Schonauer EPAC 2000 pp966-68

Main Ring Cycle

0

1

2

3

4

0 20 40 60 80 100 120

ms

RF Voltage (MV)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

B Field (T), dp/p (%)

Vrf

B

4 Booster Batches

High power beams: what for? Improve LHC beam (yet to be seen) High flux of POT for hadron physics Feed -factory


Possible parameters see H. Schonauer, April ‘03

Beam Power on Target MW 4Kinetic Energy GeV 30Transition gamma > 30Pulse frequency Hz 8.33Number of bunches 8Bunch intensity p/bunch 1.25E+13Ring physical emittance (2σ) π mmmrad 4 . 6Rin g normalised emittance (2σ) π mmmrad 15 0Longitudina l Emittance eV s 2 . 4Bun ch Lengt h (rms) n s 1 . 2Bun ch Lengt h (full) n s 5Momentum spread ± 0.0 08Distanc e between bunches n s 39 3


Technological Challenges in a 30 GeV RCS

see H. Schonauer, April ‘03

Lattice and beam dynamicsHigh t needed but difficult to have dispersion-free SS at the same timeConstraint on 1 together with =0 and large dynamic aperturePotential coupled bunch instability during the long injection plateau

RFLarge RF voltage needed, but little space for RF-cavity in dispersion-free SSInjection capture in an accelerating bucket not truly an adiabatic processDemanding HOM damperDifficult adiabatic bunch compression at 30 GeV (too low synchrotron fr.) Capture loss versus injection energy

Vacuum pipe and bean surroundingsLarge shielded ceramic chamberTight impedance budget: Z/N < 2 ohms critical

Dipoles and power suppliesLarge stored energy (some hundreds of kJ per dipole)Fast power supplies


Conclusion A staged roadmap for the LHC luminosity upgrade needs

R&D on: High-field (up to 15 T) superconducting cables and magnets Powerful and sophisticated RF devices for beam manipulations Medium-field fast-pulsed superconducting cables and magnets Accelerator design and integration to existing constraints

Upgrading LHC complex is a unique opportunity to Share technological developments with other communities such

as: Fusion (EFDA) Nuclear physics (GSI) NMR developers

Boost the CERN accelerator complex for future applications such as: High intensity hadron and neutrino physics at intermediate energy Injector developments for neutrino factory

Initial resources for R&D are presently provided by EU and CERN within the frame of CARE, in particular within the HHH-network and in the NED and the HIPPI JRAs (most likely, more support will be needed soon)


Thank-you for your attention

cern-care workshop hhh2004, 8 november 2004 technological challenges for the lhc upgrade w. scandale...

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