Design Review of the 1 st Rotatable Collimator (RC1) Prototype Project Overview 15 December 2005 Tom Markiewicz/SLAC BNL - FNAL- LBNL - SLAC US LHC Accelerator Research Program

Bureaucratic & Historical Background Information Technical detail to follow

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 3 / 34 History Jim Strait/FNAL-LARP mentions “LHC Beam-Abort Failure” collimator survival problem as potential LHC SLAC “Futures” seminar in April –NLC “consumable rotatable collimators” seem to be a possible solution –CERN colleagues & LARP contacted they are interested, discussions begin In spring 2004, CERN decides to stay with baseline design for early, less than design luminosity, LHC running (=Phase I) and install new collimators, if necessary, as current & luminosity rise to design 1E34 (=Phase II) –Discussions with CERN, LARP, DOE, & SLAC management on desire, appropriateness, resources, … of adapting SLAC consumable concept for LHC Phase II result in SLAC joining US-LARP with task of producing a beam- testable prototype by 2008 Design work in FY2005 results in CDR for prototype. LARP management wants external concurrence that prototype looks likely enough to do the job before it begins to commit serious funds. SLAC team wants educated advice on improvements, alternatives & concerns. Hence this review.

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 4 / 34

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 5 / 34 LARP FY06 Budget: 11M$ Total; 720k$ for RC1 Many projects, healthy competition

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 6 / 34 Studies of a rotatable metallic collimator for possible use in LHC Phase II Collimation System Study, design, prototype and test collimators that can be dropped into 30 reserved lattice locations as a part of the “Phase II Collimation Upgrade” required if the LHC is to reach its nominal 1E34 luminosity FY 2004:Introduction to project FY 2005:Phase II CDR and set up of a collimator lab at SLAC FY 2006:Design, construction & testing of RC1 FY 2007:Design, construction & no-beam testing of RC2 FY 2008:Ship, Install, Beam Tests of RC2 in LHC May-Oct 2008 run FY 2009: Final drawing package for CERN FY 2010:Await production & installation by CERN FY 2011:Commissioning support RC1=Mechanical Prototype; RC2: Beam Test Prototype

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 7 / 34 Total Phase II Collimation Projected Budget Money is tight, we are still early (~5%) in the project, is it worth it & are we ready to proceed?

Phase I and Phase II Collimation at LHC

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 9 / 34 LHC Collimation Requirements LHC Beam Parameters for nominal L=1E34cm -2 s -1 : –2808 bunches, 1.15E11 p/bunch, 7 TeV  350 MJ –  t=25ns,  ~200  m (collisions) System Design Requirement: Protect against quenches as beam is lost –Design shielding for expected ~30hr or 3E9 p/s or 3.4kW –Design collimator cooling for  = 1 hour or 8E10 p/s or 90kW –Plan for occasional bursts of  = 12 min or 4E11 p/s or 450kW abort if lasts > 10 sec Collimation system inefficiency: – Inefficiency ∙ Max Loss Rate < Quench Loss Rate –dQ/dV ~ 1.5mW/gm in SC coil causes quench –Estimate inefficiency of collimation system via SIXTRACK program –Determine minimum required inefficiency via FLUKA/MARS 8E6 p/s on TC will quench Q3 in triplet  2E-5 4E11 p/s loss

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 10 / 34 Betatron Collimation in IR7 –3 short (60cm) “Primary” collimators (H,V,S) at 6  –11 long (1m) “Secondary” Collimators (various angles) at 7  Momentum Collimation in IR3 –4 long (1m) “Secondary” collimators Other –1m H&V Copper Tertiary Collimators at Experimental IRs at 8.4  –1m Cu or W Absorbers at 10  –Warm Magnets, tunnel and shielding absorb remainder of lost beam energy Non-Accident Engineering Challenge –The first long secondary collimator downstream of the primary system must absorb much more energy than any other secondary in the system since % of list particles interact inelastically in the 6  primaries –The deformation specification of the collimator jaw is set at 25  m in order to maintain system efficiency The LHC Collimation System Accident Scenario When beam abort system fires asynchronously with respect to abort gap (armed HV trips accidentally) 8 full intensity bunches will impact collimator jaws

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 11 / 34 Phase I and Phase II Collimation Phase I: Use Carbon-Carbon composite as jaw material –60cm/1m Carbon undamaged in Asynchronous Beam Abort –Low energy absorption of secondary debris eases cooling & tolerances 6-7 kW in first 1m C secondary behind of primaries when dE/dt=90 kW –10 sec 450 kW load handled as a transient –Low, but adequate collimation efficiency to protect against quenches at lower L expected at startup –High, but adequate machine impedance for stable operation at low L expected at startup Phase II: Metal collimators into vacant slots behind each Phase I secondary –Good impedance and efficiency allowing LHC to reach design L= 1E34 After stable store open Carbon jaws and close Metal jaws –Jaw will be damaged: what to do? –More energy from primaries will be absorbed: cooling & deformation only pertains to one unlucky collimator per beam!

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 12 / 34 IR7 Collimator Layout 11 Carbon Phase I and 11 Metal Phase II Secondary Collimators per beam in IR7

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 13 / 34 IR7 Collimator Layout Beam Direction Primary Collimators Hard Hit Secondary Collimators

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 14 / 34 LHC Beam Dump Abort System R. Schmidt HALO ‘03

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 15 / 34 # Bunches on Collimators  Delay in Retriggering Dump Kicker J.-B. Jeanneret HALO ‘03  t now < ~0.7  s  8 bunches on colls Carbon-Carbon Jaws Chosen for Phase I as they will survive hit by 8 bunches

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 16 / 34 LHC Phase I 25x80mm 2 Carbon/Carbon Secondary Collimators cooled for 7kW DC

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 17 / 34 LHC Phase I 25x80mm 2 Carbon/Carbon Secondary Collimators w/ 7kW cooling Prototypes Made & Tested Full Order Placed

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 18 / 34 Impedance Limits Luminosity Carbon Collimators Dominate Impedance Stable Unstable

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 19 / 34 Copper Similar result was obtained by Ralph A  mann Yunhai Cai Study of Material for Secondary Collimators High Z materials improve system efficiency Copper being considered because its high thermal conductivity Available length for jaws is about 1 meter Achievable efficiency is about 3.5x10 -4 at 10  As Sixtrack program adds absorbers/tertiary collimator we expect ~x10 improvement Carbon

The SLAC Rotatable Collimator Studies and Prototype Design

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 21 / 34 R&D Plan Design a COLLIMATOR with ROTATABLE METAL JAWS –that we can cool to ~<12kW/jaw, keeping T<T FRACTURE and P H2O <~1 atm. –that has reasonable collimation system efficiency & good impedance –that satisfies mechanical space & accuracy requirements –that, when damaged by a (rare) ASYNCH. BEAM ABORT, can still rotate (max. 360°) in its to present a clean surface to the beam Scope: –Tracking studies to understand efficiency and loss maps of any proposed configuration (SixTrack) –Energy deposition studies to understand heat load under defined “normal” conditions & damage extent in accident (FLUKA) –Engineering studies for cooling & deformation (ANSYS) –Construct 2 prototypes with eventual beam test at LHC in 2008 –After technical choice by CERN, engineering support –Commissioning support after installation by CERN

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 22 / 34 SLAC NLC “Consumable Spoiler” as Prototype for Phase II LHC Secondary Collimator Differences LC / LHC: Jaw length 10cm  100cm Maximum gap & 2mm  4.5cm Power deposited 10W   12 / 60kW/jaw E. Doyle J. Frisch

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 23 / 34 Task#1: Timescale & Manpower FY 2004:Introduction to project FY 2005:Phase II CDR and set up of a collimator lab at SLAC FY 2006:Design, construction & testing of RC1 FY 2007:Design, construction & no-beam testing of RC2 FY 2008:Ship, Install, Beam Tests of RC2 in LHC May-Oct 2008 run FY 2009: Final drawing package for CERN FY 2010:Await production & installation by CERN FY 2011:Commissioning support RC1=Mechanical Prototype; RC2: Beam Test Prototype Active Manpower: Eric Doyle-Engineering Lew Keller-FLUKA Yunhai Cai-Tracking Tom Markiewicz- Integration Tor Raubenheimer-Design Planned hires: Mech. Engineer#2 Postdoc#1 Mech. Designer Future Effort: Controls Engineer

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 24 / 34 Energy Deposition in Metal Phase II Secondary Collimators w/ Carbon Phase I Collimators Open Calculated in FLUKA using CERN-provided input file Lew Keller

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 25 / 34 ANSYS 3D Time Dependent Thermal Distortion Simulations of 15cm OD, 1.2m long cylindrical jaws under 2 cooling schemes Cu, 61C  x=221 um support beam Eric Doyle

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 26 / 34 Limitations of the Design Study Focused on 12min beam lifetime (abort in 10 sec) case (450kW, 4E11p/s beam loss “transient” rate) [5x “engineering loss rate” or “steady state”, 150x “average loss rate”] where each jaw absorbed 58.5kW Absolute T of material relative to a presumed fracture temperature and well-defined melting temperature H 2 O temperature relative to 100° C & need for a high pressure system Resulting deflection due to differential thermal expansion & swelling relative to CERN specification of 25um flatness to maintain efficiency We did not verify, nor we will justify today, the 25um spec In the end we settled on a limit of 25um deflection into the beam which is understandable given 200um beam size, 7sigma collimator gap & 350 MJoule beam We did NOT focus on Accident where collimator is hit by 8 bunches with 1.15E11 p with 200um spot size –Calculations done but temperature so high that simple FLUKA probably not valid –Material destroyed but extent of damage difficult to assess by calculation –We are now VERY concerned that extent of damage region might be important –Plan more sophisticated calculations and eventual beam tests

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 27 / 34 Summary of Design Choices Materials Low Z materials absorb less E but did not deliver efficiency (C, Be, Al) Ti, W, Inconel, SuperInvar did not conduct heat well, got too hot & lost desirable properties (expansion coefficient) at high temperature Copper looked good, was easy to work with, and was our eventual choice Design Thin Cu designs did not seem to work: Very this sheets (200um Cu) were never really analyzed –without water cooling presumed to get too hot –would break in an asynchronous beam abort accident –If backed by a low Z material would blister due to differential thermal expansion 5mmCu – backed (somewhat unrealistically) by water got too hot as well »seemed dangerous in the accident scenario –Backed by Be did not perform sufficiently better to overcome anti-Be sentiment at CERN & difficulties in fabrication Solid Cu cylinder was ultimate choice, but there is NO WAY a 1m long object can meet a 25um deflection specification when it is hit by 60kW of beam

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 28 / 34 Key Compromise: Relaxed mechanical deformation specifications <25 um INTO beam guaranteed by adjustable mechanical stop(s) Ride on groove deep enough to not be damaged in accident case <400 um AWAY FROM 0.8E1p/s loss (1mm at 4E11p/s loss) Flexible support on adjustment Other possible solutions that treated the 1 st collimator downstream of primaries differently than others were inspired by FLUKA calculations that showed that the heat loading on down beam collimators decreases sharply with distance from TCSM1 and efficiency calculations that showed that removing only 1 of 11 collimators did not decrease system efficiency. –using carbon jaws for the first secondary –remove it completely –Increase its aperture from design value of 7sigma Benefit of this option would have been a cost effective relaxed cooling design good for 28/30 collimators Final decision was to go with a “as good as can be built” design because: –When jaw deflects under high load, reduced power absorption and effective collimator length approximates cases where collimator has been removed/opened –When conditions more normal, the difficult collimator can still contribute maximally –CERN is always thinking of luminosity upgrades beyond 1E34

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 29 / 34 Possible Path to Immediate RC1 Prototype: Leave TCS#1 Carbon-Carbon, Remainder Cu Inefficiency 1C-10CuAll Cu Horizontal2.84x x10 -4 Vertical3.63x x10 -4 Skew 4.57x x10 -4

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 30 / 34 Other LHC Boundary Conditions Mechanics must fit within CERN Phase I C-C envelope –224mm center-to-center with 88mm OD beampipes –1480mm longitudinal flange-to-flange –Vacuum vessel sized to provide 8mm clearance to adjacent beam and allow gross/fine 0°, 45°, 90° positions Adjustment –Gap adjustable between ±5 and ±15 sigma (2-6mm) & centered on beam –25mm adjustment/jaw (22.5mm relative to beam w/±5mm allowed beam center motion –Each jaw end independently moved in 10um steps Vacuum: <1E-7 Pa (1.3E-5 torr) RF: pass vetting by CERN “impedance police” Practical –use Phase I alignment, adjustment scheme, controls, etc. –Use Phase I 27 °C input H2O / 42 °C maximum allowed return H2O

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 31 / 34 Final Design Two 75cm Cu 136mm OD cylindrical jaws with 10cm tapered ends with axes connected to vertical mover shafts via flexible supports and a central adjustable stop Thin RF foils and 9mm end-taper for RF concerns Helical tube cooling with pressurized H2O (to prevent boiling in transient loss case) with flexible supply lines to provide 360° rotation

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 32 / 34 Studies Will Continue in Parallel with Construction Tracking Studies: Hit maps for each of 11 IR7 collimators/beam and efficiency with 60cm C-C primaries and Cylindrical 75cm jaws which includes effect of tertiary collimators and absorbers FLUKA energy deposition with 60cm primaries & cylindrical 75 cm jaws in CERN’s improved FLUKA environment ANSYS thermal shock studies for 8-bunch accident case Studies/experiments to verify –assumed extent of damage in accident Where metal slag will wind up –acceptable peak temperature of jaw for DC use Continual engineering details: see Eric Doyle’s talk

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 33 / 34 Interaction of Phase II Project with CERN Collaboration – –Monthly video meeting with active discussion –Transfer of codes, drawings & eventually sub-assemblies –Several face-to-face working meetings CERN Phase II program is beginning CERN will concentrate on alternative metal designs A decision on which course to pursue will be taken after operational experience with Phase I system, LHC performance, and beam tests of several prototype designs are considered In all cases, knowledge from SLAC Phase II prototype is deemed valuable input and regardless of final technology choice for Phase II, SLAC will participate in Phase I & Phase II commissioning.

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 34 / 34 My Wish for Your Conclusion “We find that sufficient studies have been done to justify the proposed design and that, while there are more questions to be answered and details to incorporate, given the time pressure of a 2008 run, the team must begin it’s prototype construction and testing program.” + Any comments on design variants, tests, materials, etc. that your expertise allows you to make. Thanks for your attention!

Bonus Slides

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 36 / 34 IR3 Collimator Layout

RC1 Conceptual Design Review December 2005Project Overview - T. MarkiewiczSlide n° 37 / 34 Quench Protection Sets Maximum Current Given Collimator System Inefficiency 7.6E6 7 TeV 12min 2E-5 Desired 2E-4 Phase II (assumes 1m Cu) 11E-4 Phase I Nom. I IntensityInefficiency 4E11 p/s x 2E-5 = 8E6 p/s corresponds to stated quench limit in Q3 given maximum dQ/dV