Overview of LHC conventional and advanced collimation systems - - PowerPoint PPT Presentation

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Overview of LHC conventional and advanced collimation systems - - PowerPoint PPT Presentation

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Overview of LHC conventional and advanced collimation systems Stefano Redaelli, CERN, BE-ABP on behalf the collimation team X-BEAM Workshop: Beam Dynamics meets Vacuum, Collimations and Surfaces logo 8-10 March 2017 area Karlsruhe

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SLIDE 1

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Overview of LHC conventional and advanced collimation systems

Stefano Redaelli, CERN, BE-ABP 


  • n behalf the collimation team

X-BEAM Workshop: Beam Dynamics meets Vacuum, Collimations and Surfaces 8-10 March 2017 Karlsruhe Institute of Technology, Karlsruhe, Germany

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SLIDE 2

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  • S. Redaelli, X-Beam workshop

Table of contents

▪ Introduction ▪ LHC Collimation


— Overall layout and collimator design
 — Operational cleaning performance

▪ Upgrade plans for HL-LHC


— New challenges for the upgrade 
 — Crystal collimation developments
 — Status of hollow e-lens

▪ Conclusions

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SLIDE 3

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  • S. Redaelli, X-Beam workshop

Introduction

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So far, no quenches from circulating beam losses at the LHC!

The LHC collimation system is designed to prevent superconducting magnet quenches from losses of the 360MJ LHC proton beams

LHC stored beam energy vs time in 2016 at 6.5 TeV

Record: 270MJ

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SLIDE 4

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  • S. Redaelli, X-Beam workshop

LHC collimation layout

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Total of 118 [was 108 in 
 Run I] collimators 
 (108 [was 100] movable).

Dedicated insertions for betatron (IR7) and momentum (IR3) cleaning systems. Cleaning of incoming beam
 in all experiments. Physics debris collimation
 in the high-lumi IR1/5.

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SLIDE 5

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  • S. Redaelli, X-Beam workshop

Collimator design and main features

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Beam

V a c u u m t a n k

Jaw (Carbon)

What the beam sees!

~ 2 mm

Two-jaw design: 
 Beam cannot “drift away”!

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SLIDE 6

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  • S. Redaelli, X-Beam workshop

Collimator design and main features

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Beam

V a c u u m t a n k

Jaw (Carbon)

What the beam sees!

~ 2 mm

Two-jaw design: 
 Beam cannot “drift away”!

Tunnel installation (TCT in IP2)

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SLIDE 7

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  • S. Redaelli, X-Beam workshop

New: BPM-integrated design

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  • A. Dallocchio, 

  • L. Gentini

18 new BPM collimators installed around experiments in 2014 for faster alignment and orbit monitoring.

5 10 15 20

BPM pick-up signals

5 10 15 20

Beam position [mm]

0.5 1

UP DW

5 10 15 20

Left jaw [mm]

15.5 16 16.5

LU LD

Time [s]

5 10 15 20 25

Right jaw [mm]

  • 15
  • 14.5
  • 14
  • 13.5

RU RD

  • G. Valentino

Beam centring, angular adjustment

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SLIDE 8

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  • S. Redaelli, X-Beam workshop

Collimator materials — inventory

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Bake-able to 250 deg during 24h (> 60 over 20 years) Clean, with no traces of hydrocarbons, organic and inorganic residues
 (partial pressure < 10-11 mbar) Leak tight: global helium leak rate < 10-10 mbar.l/s Outgassing rate 10-12 mbar.l/s.cm2 i.e. furnace treatment at 1000 deg
 under vacuum (carbon surface, stainless steel, ferrites …) Total outgassing rate ~ 10-7 mbar.l/s

  • V. Baglin for the vacuum team

Vacuum guidelines and requirements were taken into account from initial phases of production. Careful selection of well- qualified materials.

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SLIDE 9

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  • S. Redaelli, X-Beam workshop

Multi-stage cleaning — a beam dynamics topic

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Complex beam dynamics Material science, impedance, interaction with matter,

  • perational optimisation, …
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SLIDE 10

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  • S. Redaelli, X-Beam workshop

Betatron cleaning: simulation and measurement

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  • A. Vallone

Beam

Multi-turn cleaning process “limited” by dispersive losses in the dispersion suppressors downstream of the collimation insertion. TCLA 
 (absorbers) TCSG
 (secondary)

Beam 1

TCP
 (primary) Cleaning measurement: controlled excitation of beams (white noise in transverse damper), then plot ratio of losses:

BLMi / BLMTCP

(BLM = beam loss monitor)

  • D. Mirarchi
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SLIDE 11

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  • S. Redaelli, X-Beam workshop

Overall cleaning performance

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Beam 1

Off-momentum Dump TCTs TCTs TCTs Betatron

Vertical losses

Excellent cleaning: highest cold losses ~ 0.0001!

1e-5

  • D. Mirarchi

6.5 TeV, β* = 40 cm

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SLIDE 12

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  • S. Redaelli, X-Beam workshop

Table of contents

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▪ Introduction ▪ LHC Collimation


— Overall layout and collimator design
 — Beam cleaning performance

▪ Upgrade plans for HL-LHC


— New challenges for the upgrade
 — Crystal collimation developments
 — Status of hollow e-lens

▪ Conclusions

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SLIDE 13

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  • S. Redaelli, X-Beam workshop

HL-LHC: Scope of collimation upgrade

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Increased beam stored energy: 362MJ → 700MJ at 7 TeV


Collimation cleaning versus quench limits of superconducting magnets.
 Machine protection constraints from beam tail population
 (7 MJ above 3 sigmas even for perfect Gaussian tails!).

Larger bunch intensity (Ib=2.2x1011p) in smaller emittance (2.2 μm)


Collimation impedance versus beam stability.
 Collimator robustness against regular and abnormal beam losses
 at injection as well as top energy.

Larger p-p luminosity (1.0 x 1034cm-2s-1 → 5.0-7.5 x 1034cm-2s-1)


Need to improve the collimation of physics debris.
 Overall upgrade of the collimation layouts in the insertion regions.

Much smaller β* in the collision points (55 cm → 15 cm)


Cleaning and protection of high-luminosity insertions and physics background.

Operational efficiency is a critical for HL-LHC!


Reliability of high precision devices in high radiation environment; alignment.

Upgraded ion performance (6 x 1027cm-2s-1, i.e. 6 x nominal)

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SLIDE 14

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  • S. Redaelli, X-Beam workshop

Collimation upgrade baseline

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Ion physics debris: 
 DS collimation

Cleaning: DS coll. + 11T dipoles, 1 unit per beam

Low-impedance, high robustness secondary collimators: coated MoGr

Completely new layouts
 Novel materials: TCTs in CuCD
 IR1+IR5, per beam: 4 tertiary collimators
 3 physics debris collimators
 fixed masks

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SLIDE 15

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  • S. Redaelli, X-Beam workshop

Dispersion suppressor collimation

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Main beam dp/p<0 Collimators

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SLIDE 16

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  • S. Redaelli, X-Beam workshop

Dispersion suppressor collimation

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▪ One standard 15 m long dipole replaced with 2 shorter 11 T dipole, making space for a warm collimator in the cold region. Installation: 2020! ▪ Similar solution around ALICE detector, with collimator in connection cryostat ▪ Cold collimator option was dismissed because of vacuum arguments
 Topics for discussion: cryo collimators for future multi-100MJ beams?

Courtesy D. Duarte.

Q7 Q8 Q9 Q10

60cm active length, Tungsten alloy. Design of “TCLD” collimator finalised: 
 prototype under construction.
 Production: 4 collimator units for 2020.

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SLIDE 17

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  • S. Redaelli, X-Beam workshop

New collimator designs

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TCLD for DS TCTX/TCLX for TAXN/D2 regions TCTPW for beam-beam compensation studies

Compression

Tertiary collimator with embedded wire for long-range beam- beam MDs

New secondary collimator jaw

Vacuum of second beam?

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SLIDE 18

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  • S. Redaelli, X-Beam workshop

New collimator designs

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TCLD for DS TCTX/TCLX for TAXN/D2 regions TCTPW for beam-beam compensation studies New secondary collimator jaw

Vacuum of second beam?

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SLIDE 19

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  • S. Redaelli, X-Beam workshop

Advanced materials for future collimators

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Scope: more robust tertiary collimators; low-impedance secondaries.
 Most promising: Mo-Gr composited, with or without Mo coating.
 Copper Carbon-diamond (CuCD). Our ambitious plan: 
 Build and install 12 low-impedance collimators by 2020! Many challenges ahead (for a short time):


  • Prototype will be installed next week in the LHC.

  • Production techniques for new materials, including coating

  • Material properties under high irradiation

  • UHV behaviour of novel materials, with coating.

Mo-­‑Gr ¡composite Cu-­‑CD ¡composite Cu-­‑CD ¡Fracture ¡Analysis

Synergy : FCC collimation studies

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SLIDE 20

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  • S. Redaelli, X-Beam workshop

Status of prototyping and vacuum

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V a c u u m i s a c r i t i c a l c

  • n

c e r n ! C

  • l

l i m a t

  • r

t

  • b

e i n s t a l l e d n e x t w e e k f

  • r

b e a m t e s t s i n 2 1 7 .

MoGr block coated with TiN (yellow top) and Mo (bottom)

Novel ¡composite ¡ absorber

  • C. Accettura, F. Carra
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SLIDE 21

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  • S. Redaelli, X-Beam workshop

Table of contents

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▪ Introduction ▪ LHC Collimation


— Overall layout and collimator design
 — Beam cleaning performance

▪ Upgrade plans for HL-LHC


— New challenges for the upgrade 
 — Crystal collimation developments
 — Status of hollow e-lens

▪ Conclusions

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SLIDE 22

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  • S. Redaelli, X-Beam workshop

Advanced collimation studies

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Active halo control through hollow electron-lenses


Recent project review on HEL: acknowledged the need for active halo 
 controls at the HL-LHC and fully recommended to deploy HELs.
 Details: https://indico.cern.ch/event/567839 
 We are in the process of assessing the addition of HELs to the baseline.

Crystal collimation with bent crystals


Goals: improve ion cleaning performance 
 LHC tests: first observation of channeling at 6.5 Z TeV (proton + Pb ions).

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SLIDE 23

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  • S. Redaelli, X-Beam workshop

Hollow e-lens concept

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“Non-material” scraper — adds scraping functionality but particles are disposed of by the present collimation system. Can be installed in other points than IR7, because kicks per turn are small. Require overlap of e- and proton beam over ~3 meters.

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SLIDE 24

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  • S. Redaelli, X-Beam workshop

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Hollow e-lens design

  • D. Perini

Technical design of hollow e- lens for the HL-LHC is well advanced! All key components have been addressed. Timeline: studying a possible implementation of two lenses in 2023 (LS3)!

Magnetic shield Electrical insulation

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SLIDE 25

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  • S. Redaelli, X-Beam workshop

CERN electron gun

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2 4 6 8 10 1 2 3 4 5 Cathode−anode voltage [kV] Peak collector current [A]

  • CERN hollow electron gun prototype (CHG1)

Fermilab electron−lens test stand, 4 Jan 2017 Heater: 8.9 A, 8.6 V Solenoids: 0.1 T / 0.4 T / 0.1 T Pulse width 8 µs, rep. rate 2 Hz Perveance: 6.14 µperv

At CERN At Fermilab The first CERN hollow electron gun was tested
 in the Fermilab electron beam test-stand. Achieved output current 5.4A (new record).

Measurements by G. Stancari (FNAL).

Design goal: 5A

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SLIDE 26

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  • S. Redaelli, X-Beam workshop

Controls R&D and development for crystals

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  • A. Masi for the STI controls team

Limiting component: Optic fibre feedthrough limited to 180˚C. R&D underway with external company to develop a 220˚C compatible version.

Interfererometer optical heads with high temperature Ceramabond glue High temperature, vacuum compatible

  • ptic fibres

Rotational stage with thermal expansion compensation spring assembly and custom piezo actuator with high Curie temperature, no glue and high temperature solder for electrode wires

Piezo goniometer modifications 
 for 220˚C bakeout compatibility

First demonstration of LHC halo channeling at 6.5 TeV! 4 bent crystals in the LHC as of 2017. Studying a 1 MJ collimator absorber for proton beams

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SLIDE 27

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  • S. Redaelli, X-Beam workshop

▪ Reviewed the LHC collimation system and the main activities planned for its HL-LHC upgrade


Excellent performance of present system, and further improvements 
 needed for the upgrade.

▪ The collimation upgrade focused on improved collimator impedance, dispersion suppressor cleaning and new layouts

  • f high-luminosity interaction regions 


Highlighted some concerns related to vacuum aspects.
 Presently focused on making novel materials compatible with UHV operation.

▪ We are pushing forward new advanced collimation concepts, not yet baseline but proceeding at full steam as R&D topics


Hollow e-lenses for active halo control of 700MJ beams
 Crystal collimation, with focus on heavy ion cleaning concerns

▪ Several issues / points of contact with the communities at this workshop! 


I am looking forward to discussing further!

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Conclusions