beam Rotatable Collimators as a Possible US Contribution to the LHC Luminosity Upgrade Project 20 June 2008 LARP DOE Review Tom Markiewicz/SLAC BNL - FNAL- LBNL - SLAC US LHC Accelerator Research Program

Note With Pride

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 3 / 32 System Design Momentum Collimation Betatron Collimation C. Bracco Behind each of 30 C-C 1m secondary collimators (“Phase I, TCSG”) is an empty slot for an “improved” (Phase II) collimator

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 4 / 32 LHC Phase II Base Concept physical constraints current jaw design beam beam spacing: geometrical constraint Length available 1.47 m flange - flange Jaw translation mechanism and collimator support base: LHC Phase I >10 kW per jaw Steady State heat dissipation (material dependent) Cu coolant supply tubes twist to allow jaw rotation Hub area Glidcop Cu Mo Cantilever Mo both ends Helical cooling channels 25mm below surface 20 facets

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 5 / 32 Cu Jaw-Cu Hub-Mo Shaft Design 2mm shaft-jaw gap gives x5 improvement in thermal deformation over solid shaft-jaw design 1260 um  236 um (60kW/jaw,  12min) 426 um  84 um (12kW/jaw,  =60min) Rather than Cu, Moly shaft improves Gravity sag x3: 200 um  67 um Thermal bulge 30%: 339 um  236 um

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 6 / 32 Status of RC Program 1.Jaw support & rotation mechanism COMPLETE (June 2007) 2.First full single jaw-hub-shaft unit COMPLETE 3.Preliminary tests indicate performance in accord with FEA to ~10% Work to complete RC1: 1.Finalize RF design 2.Test a few new concepts to simplify machining & brazing process –Full length graphite choke when brazing coil to mandrel –Keystone reduction –Use 360° ¼-length jaws with braze wire rings cut on ID rather than 90° jaws –Anything to reduce number mating surface prep requirements for brazes 3.Order parts for 2-3 new jaws: copper mandrels, Mo shafts, Glidcop® jaws 4.Fab & braze 2-jaws, 4-supports, RF features in new vacuum tank 5.Metrology & vacuum tests 6.Mechanical motion tests on existing CERN system 7.Ship to CERN

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 7 / 32 Final Jaw Braze 22 April 2008

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 8 / 32 9kW External Heater Thermal Test Setup Heater cable Water flow control Jaw in support stand Heaters strapped on jaw Water flow tube Extra heater

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 9 / 32 Comparison of Sagitta & Temperature with ANSYS as a function of angle wit respect to heater Jaw with two 5 kW heaters modeled Includes accurate representation of Water flow/temp change Material properties Thermal expansion Heat flow / thermal conductivity Data ~10% larger than ANSYS

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 10 / 32 Performance Risks Will thermal-mechanical testing of the first jaw validate the shaft-hub- jaw design that should limit maximum jaw deflection into the beam area to 230 microns for 10 second bursts of 60kW beam absorption Will the mechanical accuracy of the device be adequate (40 um) Will the basic jaw-adjustment and jaw-rotation work as planned Will the effective impedance and RF characteristics of the jaw and the transition to the vacuum tank aperture be adequate Will the device vacuum be sufficiently low When damaged by an aborted beam, will the extent of damage be sufficiently localized to allow rotation to a clean surface, as planned

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 11 / 32 RF Design Low resistance RF contact Slot for Spiral RF Spring Short RF Test Jaw with End Socket mounted Bearing Race SiN4 balls UNDER STUDY Contact Resistance Measurements Stretched Wire Impedance Measurements Trapped mode study using Omega3P

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 12 / 32 Braze Test #3: Vacuum tests: No improvement 3rd Jaw Braze Test Assembly has been vacuum baked at 300°C for 32 hours. Results in slightly lower pressure. Inclusion of longitudinal grooves in the inner length of jaws for better outgasing Test Chamber setup similar to previous test. 2 nd 20cm Prototype 3 rd 20cm Prototype Baseline3.2E-9 Torr2.4E-9 Torr?? w/ jaw assy.3.7E-9 Torr3.4E-9 Torr Presumed jaw assy. pressure 4.5E-10 Torr10E-10 Torr?? LHC requirement 7.5E-10 Torr

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 13 / 32 Exact Nature & Extent of Damaged Region Thin Cu sample in FFTB electron beam at SLAC Hole = Beam Size 2000um 500 kW 20 GeV e- beam hitting a 30cm Cu block a few mm from edge for 1.3 sec (0.65 MJ) FNAL Collimator with.5 MJ

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 14 / 32 Accident Case: Permanent deformation AND Molten copper Case: beam abort system fires asynchronously, 8 full intensity bunches into jaw Model: - increased resolution 3-D ANSYS & FLUKA models - Thermal heating/cooling analysis followed by quasi-static stress analysis - Jaw ends constrained in z during 200 ns, released for 60 sec cool-down MJ deposited in 200 ns - Molten material removed from model after 200 ns Result: - 57e3 peak temperature (ultra fine model) - 54  m permanent deformation (concave) 5mm melt 2.5mm x 2.5mm elements T max = 57 e3 Shower max – extent of melted zone 3.3mm Cooling tubes Shaft Jaw facets

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 15 / 32 RC Ready for “Production” in FY2010 RC Design essentially complete and first jaw constructed and tests according to calculation. In principle all procedures, methods, parts finalized and need only “push the button” to fabricate first full prototype. Beam tests in will hopefully remove remaining technical risk factors. Destructive testing of the by-design damageable Copper may be prove extensive enough to remove RC from consideration Procedures, tooling, Q/C facilities for “large” production run could be developed in parallel with production of the first full prototype in FY2009, if desired.

Point With Alarm

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 17 / 32 The Problem Suggesting that the US manufactures 36 of these devices for the 30 reserved Phase II secondary collimator lattice slots (plus 6 spares) Ignores the CERN collimation “White Paper” plan calling for construction and mechanical, vacuum & beam testing of three “complementary” designs (SLAC RC, CERN High Z, CERN Low Z with coating) that can bring LHC luminosity from to before a production decision is made –The Cu secondary RCs do not give x10 improvement in luminosity When originally proposed LARP RC was to help get from <1E34 to 1E34 proton L Improved “local” collimation efficiency calculations point to –Beam intensity limited by protons that MISS all secondary collimators & quench SC magnets in “dispersion suppressor” down-beam of IR7 collimation »Local protection of these magnets by new “Cryogenic collimators” in the SC part of LHC »More efficient PRIMARY collimators (Crystals, Electron lens, …for example) –“Final” opportunity to solve all remaining collimation issues: set up time (install beam pickups into collimator jaws) ion collimation correct any remaining mechanical issues from phase I (rack & pinion + motor redesign) –Impedance limitations through means other than low resistivity metal Beam-based feedback & Landau damping Increased triplet apertures, cryo-collimators may allow fewer or larger gap collimators Does not address adequately the quality control issues seen in CERN’s Phase I collimator production nor has there yet been any talk or agreement with CERN on interface, installation, or engineering support issues.

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 18 / 32 Efficiency Studies Chiara Bracco (CERN) Performance (Efficiency) of collimation system depends on # particles getting into the cold aperture (>10  ) per unit length as a function of location around the LHC given the optics model AND an aperture model 500E6 Halo protons tracked over 200 turns in 10cm steps by Bracco et al to get loss maps for each magnet Beam intensity limitations are due to losses in the dispersion suppressor above the quench limit. Phase I to II Global Improvement Phase I Beam Intensity Limit

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 19 / 32 Intensity Limit at “Dispersion Suppressor” with Phase II at Nominal Collimation Settings Chiara Bracco (CERN) Losses due to particles that hit primaries but that do not see the secondaries While philosophy is every bit helps (take the x3.6) “ultimate” luminosity may require different collimation settings or completely different collimators (crystals as primaries?)

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 20 / 32 Cryogenic Collimators in Beam1 Dispersion Suppressor Copper secondaries set to nominal 7  settings Carbon secondaries set to relaxed opening (26.5  ) Cryogenic collimators (material copper, length 1m) placed at 300m and 387m from IR7 at 15 . Peak reduced by a factor > 30. T. Weiler/CERN

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 21 / 32 Graphite -> Copper Switching to copper will decrease the imaginary part of the impedance but increase the real part This is either good or bad depending on how you want to damp beam instabilities (Landau Damping versus Feedback) So, impedance still dominated by copper collimators

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 22 / 32 References for CERN Planning Executive Summary Second Phase LHC Collimators R. Assmann Description Phase 2 Collimator Project R. Assmann Collimation Issues for the Two LHC+ Scenarios and Future Plans R. Assmann Beam’

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 23 / 32 White Paper Plan 1.The R&D and prototyping of at least three different concepts for advanced collimation designs, each addressing different possible limitations to LHC luminosity. 2.Operational experience of the LHC with the Phase I collimation system to understand the nature of any luminosity limit and the best ways to ameliorate deleterious effects with already installed systems. 3.Testing of prototypes at CERN to their technological limits before any installation in the LHC 4.Installation and testing of qualified Phase II prototypes in the LHC during the second full year of LHC operation with a decision on phase II design and production, which may require more than one technology, at the end of the year. 5.Production of the collimators during years 3-4 of LHC operation, installation during regularly scheduled shutdowns and use beginning with year 5 of LHC operation.

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 24 / 32 White Paper Schedule Technology Decision Fall 2010 Construction Installation 2013 Run

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 25 / 32 CERN Phase II R&D Budget

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 26 / 32 CERN Pre-Production Manpower vs. Time

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 27 / 32 Production Estimated at 8M CHF

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 28 / 32 My Opinion LARP, through SLAC, is participating fully in the Phase II Collimation project as outlined in the CERN “White Paper” plan and any action on LARP’s part that looks, as this does, like it is circumventing the agreed to schedule damages our relationship with our colleagues and is doomed to failure. If, after the R&D process concludes in October 2010, a decision is made to produce some number of rotatable copper collimators, SLAC is ready to participate. This exercise should only be taken at the “CD-0” level: mission need and ballpark cost estimate, and is hopefully, laying the bureaucratic groundwork for eventual US participation in construction of collimators

Ask for Money

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 30 / 32 Unscrubbed Unit Cost Based on work done to date: $250k

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 31 / 32 Project Cost “x2 Estimate” Unit Cost for Tank, 2 jaws, rotation & support, RF$250k Unit Cost for Rack & pinion, motors, LVDTs$50k These below are probably underestimates: Assembly, test & qualification at SLAC4 FTEs 36 units over 2 years$200k EDI&A6 FTE Lab overhead42% LAUC Proposal specifies 4+1 RCs Saturate the LAUC $ request to maximum allowed We don’t know how many if any RCs will be part of the final plan

LARP DOE Review - 20 June 2008Rotatable Collimator CP Proposal - T. MarkiewiczSlide n° 32 / 32 Project Schedule Dominated by braze operations and braze oven cycles 72 jaws with 3 braze cycles per jaw –2 years for production is aggressive but possible –1 year construction seems impossible