Review on PSB 160 MeV H- Injection

9 Nov 2011, 09:00 → 10 Nov 2011, 12:00 Europe/Zurich

30/7-018 - Kjell Johnsen Auditorium (CERN)

PLUM Michael A (Oak Ridge National Laboratory)

CERN is currently designing a new H- charge-exchange injection system for the PSB, to inject the 160 MeV H- beam from the new LINAC4. The purpose of this review is to validate the engineering design of the injection equipment, to eliminate all outstanding questions, and to examine the feasibility of the proposed injection system commissioning strategy and its timeline.

- 160 MeV H- Injection into the CERN PSB The H- beam from the proposed LINAC4 will be injected into the four existing rings of the PS Booster at 160 MeV. A substantial upgrade of the injection region is required, including the modification of the beam distribution system and the construction of a new H- injection system. This paper discusses beam dynamics and hardware requirements and presents the results of optimisation studies of the injection process for different beam characteristics and scenarios. The resulting conceptual design of the injection region is presented, together with the main hardware modifications and performance specifications.

- Dump and Current Measurement of Unstripped H`ions at the Injection from the Cern LINAC4 Into the PS Booster Linac4 is the new H- linear accelerator under construction at CERN aiming to double the brightness of the beam injected to the CERN PS Booster (PSB) for delivering proton beams to experiments or further CERN accelerators, down to the LHC. The injection system in the PSB is based on the H- charge exchange where the 160 MeV H- beam is converted into an H+ beam by stripping the electrons with a carbon foil. A beam dump located inside a pulsed magnet for the injection bump will intercept the unstripped ions (H0 and H-) and measure the collected charge to detect the relative efficiency and degradation of the stripping foil. The challenge of the dump design is to meet the requirements of a beam dump providing a current measurement and at the same time minimizing the perturbation of the magnetic field of the surrounding pulsed magnet. This paper describes all phases of the dump design and the main issues related to its integration in the line.

- Lattice issues of the PS with H- charge exchange injection hardware The motivation for the construction of CERN Linac4 is to improve the performance of the PSB by raising the injection energy and implementing a new H- charge exchange multiturn injection scheme. Lattice perturbations introduced by the new injection hardware are described. Strategies to mitigate the consequences, first by minimizing the additional focusing introduced and, by compensating the residual perturbation, are reported.

- Layout considerations for the PSB H- injection system The layout of the PSB H- injection system is described, including the arguments for the geometry and the required equipment performance parameters. The longitudinal positions of the main elements are specified, together with the injected and circulating beam axes. The assumptions used in determining the geometry are listed.

- Linac4 Technical Design Report Linac4 is an H- linear accelerator, intended to replace Linac2 as injector to the PS Booster (PSB). By delivering to the PSB a beam at 160 MeV energy, Linac4 will provide the conditions to double the brightness and intensity of the beam from the PSB, thus removing the first bottleneck towards higher brightness for the LHC and simplifying operation. Moreover, this new linac constitutes an essential component of any of the envisaged LHC upgrade scenarios and could open the way to future extensions of the CERN accelerator complex towards higher performance. This Technical Design Report presents a detailed technical overview of the Linac4 design as it stands at end 2006.

- Operational considerations for the PSB H- injection system For the LINAC4 project the PS Booster (PSB) injection system will be upgraded. The 160 MeV H- beam will be distributed to the 4 superimposed PSB synchrotron rings and horizontally injected by means of an H- chargeexchange system. Operational considerations for the injection system are presented, including expected beam losses from unwanted field stripping of H- and excited H0 and foil scattering, possible injection failure cases and expected stripping foil lifetimes. Loading assumptions for the internal beam dumps are discussed together with estimates of doses on various components.

- Stripping foil issues for H- injection into PSB at 160 MeV Beam physics considerations for the stripping foil of the 160 MeV PSB H- injection system are described, including the arguments for the foil type, thickness, geometry and positioning. The foil performance considerations are described, including expected stripping efficiency, emittance growth, energy straggling, temperature and lifetime. The different beam loss mechanisms are quantified in the context of the aperture limits, operational considerations and collimation requirements.

- Stripping foils for the PSB H- injection system Beam physics considerations for the stripping foil of the PSB H- injection system are described, including the arguments for the foil type, thickness, geometry and positioning. The foil performance considerations are described, including expected stripping efficiency, emittance growth, energy straggling, temperature and lifetime. The required movement ranges and tolerances are detailed, together with the assumptions used.

Wednesday 9 November

1 Welcome and Introduction to LIU Project

CERN has recently built the Large Hadron Collider (LHC), a superconducting circular particle accelerator designed for colliding two proton beams at 7 TeV energy. In order for the LHC to achieve ultimate beam parameters, CERN has launched a long-term program for the progressive replacement or upgrade of the old chain of accelerators presently used as injectors for the LHC, the so-called LHC Injectors Upgrade (LIU) project, and Linac4 is the first element of this program. Linac4 is a linear accelerator for negative hydrogen ions, which will replace the old Linac2 as linear injector for the CERN PS Booster. The 160 MeV H- beam from Linac4 will be injected into the 4 superimposed rings of the PS Booster by means of charge-exchange injection using, for each PSB ring, a set of 4 pulsed dipole magnets creating the required injection bump. A carbon stripping foil in the injection region will convert the H- beam to H+. The presentation gives an introduction to the plans for the upgrade of the PS Booster within the LIU project with focus on the modification of the injection region.

Speaker: Dr Klaus Hanke (CERN)

Slides

• intro_v3.pdf
• intro_v4.pdf
• intro_v4.pptx

2 PSB H- Injection Concept

Speaker: Dr Brennan Goddard (CERN)

Slides LIU-PBU-PSB-Injection-Review.pdf LIU-PBU-PSB-Injection-Review.pptx

3 Painting, injection matching, emittances and beam dynamics

An overview on the new PSB H- injection system is presented in this talk. The principle of longitudinal painting, consisting in energy modulation from Linac4, is introduced. Transverse painting in the horizontal plane, by means of four existing PSB kicker magnets (KSW), is described. Results of extensive and detailed beam dynamic studies allowed to precisely define the KSW generators waveforms fulfilling the requirements in intensities and emittances of all the PSB users. Preliminary studies have been carried out to evaluate how to obtain the required vertical emittance and the option of a transverse painting, also in the vertical plane, is explored.

Speaker: Dr Chiara Bracco (CERN)

Transparents LIU-PBU-PSB-Injection-Review-Cbracco_final.pdf LIU-PBU-PSB-Injection-Review-Cbracco_final.pptx

4 BSW Chicane Magnets

Per PS Booster ring, 4 outside vacuum magnets will be installed to provide the injection bump through the stripping foil. The first magnet is a septum and the following magnets are window frame dipoles, of which the last has to cope with the unstripped particle beam dumps. The talk will describe the constraints imposed on these injection chicane magnets and present the baseline implementation.

Speaker: Mr Jan Borburgh (CERN)

Slides BSW_magnet_presentation.pdf BSW_magnet_presentation.pptx

10:30 Coffee Break

5 KSW Painting magnets

Speaker: Luis Miguel Coralejo Feliciano (CERN)

Slides LIU-PBU-PSB-Injection-Review_v2.pdf LIU-PBU-PSB-Injection-Review_v2.pptm

6 Internal H0/- Dump

The conceptual ideas for the dumping of the unstripped H0 and H- ions coming from the PSB injection region at the energy and beam parameters due to the Linac4 future connection is presented in this talk. The dump core itself covers longitudinally the second half of the BSW4 chicane magnet, close by but out of the trajectory of the circulating H+ beam. Due to dimension constraints and the heat load to the core, the dump has to be actively cooled via the back-flange possibly without any feed-through, which impose the need to guarantee the good holding of the core together with the good thermal contact between the flange and the core itself. Specifications, parameters, layout and constraint are presented. First results based on studies on activation as well as thermo-mechanical behaviour are also presented and discussed. Finally standing questions and issues are addressed.

Speaker: Cesare Maglioni (CERN)

Slides

• LIU-PBU-PSB-Injection-Review_Maglioni.pdf
• LIU-PBU-PSB-Injection-Review_Maglioni.pptm
• LIU-PBU-PSB-Injection-Review_Maglioni.pptx

7 Injection foils and handling system

The linac4 beam will be injected horizontally into the PSB by means of an H- charge-exchange injection system using a graphite stripping foil to paint the beam into the required emittance. This presentation will describes the hardware requirements and constraints, the performance specifications of the stripping foil and the conceptual design of the foil exchange unit and motorisation.

Speaker: Wim Weterings (CERN)

Slides Injection_foils_and_handling_system.pdf Injection_foils_and_handling_system.pptx

8 PSB H- Injection Vacuum analysis

The Vacuum analysis for the PSB H- injection has been done by means of the electrical network – vacuum analogy: through this method it’s possible to design complex vacuum line, taking into account the gas loads, the conductances, the pumping speeds applied and the target pressure to reach. This presentation shows how the main gas sources have been taken into account (water degassing from inner surfaces, thermal degassing from the dump, ion induced desorption, beam losses, etc.) in order to define the issues to reach the target pressure of 5e-9 mbar.

Speaker: Mrs Chiara Pasquino (CERN)

Slides LIU-PBU-PSB-Injection-Review.pptm

12:15 Lunch Break

9 Beam Instrumentation in the BOOSTER injection region

Beam instrumentation is essential for the commissioning phase of the PSB injection zone with the Linac4 beam, and for routine operation later on. The following observables are requested for that purpose: Beam profiles for steering and injection matching. The stripping efficiency is also monitored downstream the foil, in addition to the visual inspection of the foil. A fast machine protection system coupled with beam loss monitors is needed too. In this talk, analysis and solutions based on specifications issued by the machine physicists are proposed by the Beam Instrumentation Group. This very preliminary phase arouse a set of questions which needs deeper investigations.

Speaker: Jocelyn Tan (CERN)

Transparents 2011-11-09-PSB_INJECTION-Review2.pdf 2011-11-09-PSB_INJECTION-Review2.pptx

10 Beam losses

Speaker: Christian Carli (CERN)

Slides Injection_Review_11_11_09.pdf Injection_Review_11_11_09.pptx

11 Commissioning strategy and timeline

The novel H- injection of Linac4 into the PS Booster will require a complete rebuilding of the PSB injection section. The connection is presently foreseen to be ready for late 2015. 3 months must be available for installation of the new injection equipment and related machine modifications after one month of radiation cool-down, followed by 3 months of beam commissioning. The presentation will mention the dry run tests that will close up the installation phase and will define the starting conditions for beam commissioning. This has been divided up in 4 distinct phases; for each of these phases the required starting conditions will be mentioned and planned measurements and adjustments described in detail.

Speaker: Dr Bettina Mikulec (CERN)

Slides PSB_H-_injection_system_commissioning.pdf PSB_H-_injection_system_commissioning.ppt

15:30 Coffee Break

12 Questions by Reviewers, and discussions with experts

Thursday 10 November

Closed Session

Review panel discussion

10:30 Coffee Break

Review Closing Remarks

13 Review Closing Remarks

Speaker: Michael A PLUM (OAK RIDGE NATIONAL LABORATORY)

Slides

• Closeout_final.pdf
• Closeout_r1.pdf
• Closeout_r1.pptx