# Presentation: 745524

## SLAC Phase II Secondary Collimators

- 6 October 2005
- LARP Collaboration Meeting-St. Charles, IL
- Tom MarkiewiczSLAC

*BNL - FNAL- LBNL - SLAC*

_**US LHC Accelerator Research Program**_

## Task#1: Studies of a Rotatable Metallic Collimator for Possible Use in LHC Phase II Collimation System

- If we ALLOW (rare) ASYNCH. BEAM ABORTS to DAMAGE METAL JAWS, is it possible to build a ROTATING COLLIMATOR
- that we can cool to ~<10kW, keeping T<TFRACTURE and PH2O<1 atm.
- that has reasonable collimation system efficiency
- that satisfies mechanical space & accuracy requirements

- 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 & MARS)
- Engineering studies for cooling & deformation
- Construct 2 prototypes with eventual beam test at LHC in 2008
- After technical choice by CERN, engineering support
- Commissioning support after installation by CERN

## 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**

- Engineer#2
- Postdoc#1

- Active Manpower:
- Eric Doyle-Engineering
- Lew Keller-FLUKA
- Yunhai Cai-Tracking
- Tom Markiewicz- Integration

- Meeting/advice:
- Tor Raubenheimer
- Andrei Seryi
- Joe Frisch

- Planned hires:
- Mech. Engineer#2
- Postdoc#1

- Future Effort:
- Controls Engineer
- Designer

## 2005-06-01 DOE Review of Collimation Program: A+

- "The activity in collimation is impressive, with the work being approached in a very professional manner. It is a critical problem, and solving it will have great impact on the ability of the LHC to reach design luminosity. Even the task sheets for this project were done very professionally, lending confidence in a well-managed and well-focused activity. (The synergy with the ILC is clearly evident here.)"

## Status of Phase II Collimator Conceptual Designat 2005-06-01 DOE Review

- Adequate software in place and MANY studies have been done but ...
- We do NOT yet have a conceptual design for the 1st of the 11 collimators needed (per beam) in IR7
- 28 of 30 Phase II collimators will not have a heating problem
- No magic design or material which could simultaneously provide good efficiency with combination of energy absorption, thermal conductivity, & thermal expansion to maintain 25 um flatness tolerance over length of jaw during 1hr/12min (90/450kW) beam lifetime transients for nominal jaw length (1m) and gap setting (7)
- Focus on
- 150mm O.D. 25mm wall Cu jaws with helical cooling tubes
- 150mm O.D. “solid” Cu jaws cooled with axial flow over 36° of arc

## Study of Material for Secondary Collimators

- 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 is about 1 meter
-      Achievable efficiency is about 3.5x10-4 at 10 
- As Sixtrack program adds absorbers/tertiary collimator we expect ~x10 improvement

## Energy Deposition in Metal Phase II Secondary Collimators w/ Carbon Phase I Collimators Open Calculated in FLUKA using CERN-provided input file

## Power absorbed in one TCSH1 jaw at 10 when 80% (5%) of 450kW of primary beam interacts in TCPV (TCSH1)

## Helical and axial cooling channels

## ANSYS thermal and structural results for full ID cooling and limited cooling arc showing 64% less distortion with limited cooling                     

- ANSYS thermal and structural results for full ID cooling and limited cooling arc showing 64% less distortion with limited cooling**                     **

- 61C

- x=221 m
- Spec: 25m

- support

- support

- 89C

- x=79 m

- Note more swelling than bending

- Note transverse gradient causes bending

- Note axial gradient

- 64% less distortion

- _360__°__ cooling of I.D_.

- _36__°__ cooling arc_

## Material Comparison SS & Transient Thermal Deflection ANSYS simulation results for 150mm OD x 100mm ID x 1.2m L

- Material Comparison SS & Transient Thermal Deflection ANSYS simulation results for 150mm OD x 100mm ID x 1.2m L

- Notes:
- BeCu is a made-up alloy with 6% Cu.  We believe it could be made if warranted
- 2219 Al is an alloy containing 6% Cu
- Cu/Be is a bimetallic jaw consisting of a 5mm Cu outer layer and a 20mm Be inner layer
- Cu – 5 mm is a thin walled Cu jaw
- Super Invar loses its low CTE above 200C, so the 152um deflection is not valid
- Heat flux to water of 10^6W/m^2 or greater is in regime of possible film boiling

## Material evaluations compared to Cu  based on 150mm x 1200mm x25mm wall model

| Material | Reasons for rejection in favor of Copper |
| --- | --- |
| BeCu (6% Cu-loaded Be) | Beryllium is forbidden by CERN management, low cleaning efficiency due to few particles absorbed; fabrication difficulty |
| Super Invar | Poor thermal conductivity  high temperature (866°C), desirable properties (low thermal expansion coefficient) disappear at 200°C  |
| Inconel 718 | Poor thermal conductivity  high temperature (Tmp = 1400°C < 1520°C transient peak) & very high deflection (1039um SS, 1509um transient) |
| Titanium | Poor thermal conductivity  deflection 2.7 x Cu (591um, SS) |
| Aluminum | Relatively poor cleaning efficiency, water channel fabrication difficulty	 |
| Tungsten | High temperature on water side (240°C - 30bar to suppress boiling); high power density - can't transfer without boiling |

## Directions under investigation & negotiation at time of 2005-06-01 DOE Review

- Redefine secondary hybrid system to treat 1st collimator as special
- Break 1st secondary into two (unequal?) lengths of perhaps different materials
- Grooved “expansion slots” to limit deformation
- Adjust gaps of the first carbon & metal secondary to reduce heat load while maintaining efficiency with remainder of secondary system
- Keep 1st  C-C secondary collimator’s jaws at 7 and leave out 1st metal secondary collimator
- Relax deformation tolerance relaxed to if jaws expand AWAY from beam
- Begin to deal with LHC infrastructure & operational constraints
- 45mm jaw gap at injection incompatible with NLC inspired circumferentially mounted gap adjustor
- Look into adopting Phase I adjustment mechanism
- Spatial constraints of LHC beam pipes & tunnel a challenge
- Jaw dimensions, tank dimension

## IR7 Collimator Layout

- Beam Direction

- Primary Collimators

- Hard Hit Secondary Collimators

## Possible Path to Immediate RC1 Prototype: Leave TCS#1 Carbon-Carbon, Remainder Cu

| Inefficiency |   1C-10Cu | All Cu |
| --- | --- | --- |
| Horizontal | 2.84x10-4  | 3.72x10-4  |
| Vertical | 3.63x10-4   | 4.36x10-4  |
| Skew |   4.57x10-4   |   3.85x10-4  |

## Concentrating E_dep in Front Part of Jaw

## Deflections referred to shaft

- Notes:
- “Solid” jaws – 150mm OD x ~24mm ID.  Basic jaw 120cm L
- Aperture transition from 10 to 7
- 7cases based on CERN ray files for interactions in TCPV
- pre-radiator not used – Phase I carbon jaw to concentrate energy toward front of Phase II jaw.

- Effect of: shortened jaws, wider gap, jaw support scheme

- Deflections referred to edge

- basic jaw 120cm L

## Circumferential grooves reduce bending deflection by interrupting continuity of thermal strain. 

| Case | Tmax °C | Deflection (um) |  |
| --- | --- | --- | --- |
|  |  | Jaw edge ref | axis ref |
| Straight | 59.5 | 33 | ~100 |
| grooved | 59.5 | 15 | ~74 |

- Parameters
- 150mm O.D., 25mm wall, 120cm long
- Grooves: 10mm deep, 50mm spacing
- 10kW heat, evenly distributed
- 45 deg cooling arc

## Mechanical Model 2005-06-01 Used NLC Concept of Central Strongback with mid-collimator  jaw gap adjuster

## June 15-17 CERN/SLAC Collaboration Meeting

- Attendees
- CERN: Ralph Assmann (Project Leader, Tracking), Allesandro Bertarelli (Mechanical Eng.), Markus Brugger (Radiation Issues), Mario Santana (FLUKA)
- SLAC: Tom Markiewicz, Eric Doyle (ME), Lew Keller (FLUKA), Yunhai Cai (Tracking), Tor Raubenheimer
- Radiation Physics Group: Alberto Fasso, Heinz Vincke
- Results
- Agreement on basic design of RC1 (1st rotatable prototype)
- Transfer of many of CERN mechanical CAD files
- Lists of
- Further studies required
- Outstanding Engineering Issues requiring more design work
- Project Milestone List & Action Items List
- Test Installation of “New FLUKA”

## Conceptual Design of RC1 (1 of 2)

- Mechanics must fit within CERN Phase I C-C envelope
- 224mm center-to-center with 88mm OD beampipes
- 1480mm longitudinal flange-to-flange
- 25mm adjustment/jaw (22.5mm relative to beam w/±5mm allowed beam center motion
-  and use Phase I alignment and adjustment scheme
- Two 75cm Cu cylindrical jaws with 10cm tapered ends, 95cm overall length with axes connected to vertical mover shafts
- 136mm OD with 9mm taper
- Each jaw end independently moved in 10um steps
- Vacuum vessel sized to provide 8mm clearance to adjacent beam and allow gross/fine 0°, 45°, 90° positions
- 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
- Adjustable between ±5 and ±15 sigma (2-6mm) & centered on beam
- <325 um (750um) AWAY FROM beam @ 0.8E1p/s loss (4E11p/s)
- Flexible support on adjustment

## Conceptual Design of RC1 (2 of 2)

- Assumed worst case heat load (FLUKA)
- 11.3 kW/jaw steady state, 56.5kW/jaw transient (10 sec)
- Cooling boundary conditions
- 200 °C maximum temperature of Cu
- 27 °C input H2O temperature
- 42 °C maximum allowed return H2O temperature
- Two Cooling Schemes under consideration
- Helical tube: more secure H2O-vacuum interface
- Axial channels w/ diverter: superior thermal  mechanical performance
- Sufficient pressure (3 atm.) to prevent local boiling in transient
- Flexible supply lines to provide 360° rotation
- Other
- Vacuum: <1E-7 Pa (1.3E-5 torr)
- RF: shielding scheme has been proposed

## Proposed layout: 136mm diameter x 950mm long jaws, vacuum tank, jaw support mechanism and support base derived from CERN Phase I

## Vacuum tank enlarged to accommodate jaw motion.  Relative location of opposing beam pipe – near interference in skew orientations 10° deviation

- Vacuum tank enlarged to accommodate jaw motion.  Relative location of opposing beam pipe – near interference in skew orientations 10° deviation

## Helical cooling passages – fabrication concept

**Based on CERN’s design – no weld or braze between water & vacuum**

- Tube formed as helix, slightly smaller O.D. than jaw I.D.
- O.D. of helix wrapped with braze metal shim
- Helix inserted into bore, two ends twisted wrt each other to expand, ensure contact
- Fixture (not shown) holds twist during heat cycle

- Variations:
- Pitch may vary with length to concentrate cooling
- Two parallel helixes to double flow
- Spacer between coils adds thermal mass, strength
- Electroform jaw body onto coil

**Helical cooling passages – fabrication concept**

## Adjustable central gap-defining stop

- Stop prevents gap closing as jaw bows inward due to heat
- Jaw ends spring-loaded to the table assemby ... move outward in response to bowing
- May use two stops to control tilt
- Slot deep enough to avoid damage in accident
- Stop far enough from beam to never be damaged & is out of way at injection

## Swelling vs. bending deflectionEffect depends on jaw support scheme

## Flexible end supports used in conjunction with central gap-defining mechanism

- Self aligning bearing

- Leaf springs allow jaw end motion up to 1mm away from beam

- Adjustable central jaw stops (not shown) define gap
- Flexible bearing supports allow jaw thermal distortion *away from beam*

- CERN’s jaw support/positioning mechanism.  Vacuum tank, bellows, steppers not shown.

## RF Contact Overview

**RF Contact Overview**

## RF contacts – cutaway view

## RF contact variation removes step

## Jaw Support Concept – unresolved issues interferences with RF parts

**Jaw Support Concept** – **unresolved issues** interferences with RF parts

## Flex cooling supply tube concept

## Detail of flex cooling supply tube

- Contiguous with helical tube inside jaw.
- Formed after assembly-brazing of jaw and installation of bearing on stub-shaft
- Exits through support shaft per CERN design
- Material: CuNi10Fe1, 10mm O.D., 8mm I.D.

- Stub-shaft (bearing not shown)

- Support shaft

| Relaxed            (as shown) | # coils | 4 |
| --- | --- | --- |
|  | O.D. | 111mm (4.4in) |
| full 360° rotation | # coils | 5 |
|  | O.D. | 91mm (3.6in) |
|  | torque | 9.1N-m (81in-lb) |

## Power Deposition on First 120cm Secondary Collimator in 12 Min. Lifetime from 20cm C primary hit files (kW per jaw)            

| 
Primary
Collimator
  (source) | TCSM.B6.L7
      Jaws at 7  |  | 
TCSM.B6.L7
      Jaws at 10  |  |
| --- | --- | --- | --- | --- |
|  |  Copper |    Al_2219 |     Copper |  Al_2219 |
| TCP.D6.L7
   (TCPV) |         73 |         26 |         51 |         19 |
| TCP.C6.L7
   (TCPH) |         61 |         22 |         49 |         19 |
| TCP.B6.L7
   (TCPS) |         92 |         28 |         56 |         20 |

**Power Deposition on First 120cm Secondary Collimator in 12 Min. Lifetime from 20cm C primary hit files** **(kW per jaw)  **

- _Notes_:
- 1. Collimator data, ray files, and loss maps from LHC Collimator web page, Feb. 2005.
- 2.  Must add contribution from direct hits on secondary jaws.

**Sensitivity to aperture and to source of halo:**** H, V, or S**

- 56.5kW/jaw (11.3kW/jaw for 1 hr beam lifetime) assuming 80%-5% interaction ratio split from 20cm primary hit maps, but adjusting for hadron absorption in back 40cm of C primaries and adjusting for shorter 95cm length

**Notes:**
120 cm long collimator

## Continuing evolution of ANSYS model to include realistic cooling channels and cooling water response to heat generated by beam

- “Solid” jaw has less T across diameter and short cut for heat flow

**H2O simulation – helical flow shown**
- Fluid pipe elements:
- Water temperature responds to heat absorbed from jaw
- More realistic simulation
- Axial pipes can simulate axial flow
- Friction can be simulated

## Compact (136x950) jaw variations - performance comparison

## Final Expected Performance of RC1 Design

## Outstanding RC1 Unresolved Issues

- Jaw positioning
- Acceptance of estimated deflection by CERN:281/869um
- Design concept for central stop: gap adjust, 5 central position float,..
- Bearings & springs attaching jaws to vertical movers
- Load capacity of steppers
- Jaw alignment perpendicular to collimation direction
- Jaw rotation
- Specification of mechanism on crowded jaw
- Force required to rotate jaws against cooling coil
- Misc
- Spring arrangement for H, V, S orientations
- Springs to ensure that device fails open
- Motors, cables, temperature sensors, position probes, ...
- Cooling
- Possible local boiling in transient condition & need for P~3 atm. H2O system
- More flexible yet vacuum safe water supply for helical cooling
- Vacuum safe water connection/diverter for axial cooling scheme

## Other Studies Planned

- 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 Complete self consistent package of tracking, FLUKA & ANSYS results to support design choices unambiguously
- Better definition of RC1 thermal tests
- Remnant & Prompt Dose Rate calculations
- Engineer damage assessment mechanism into design
- Thermal shock studies
- Studies/experiments to verify
- assumed extent of damage in accident
- Where metal slag will wind up
- acceptable peak temperature of jaw

## What is the damage area in a missteering accident?

**2.5 cm**

**Missteered beam (9E11 protons)**
**on secondary Jaw**

**Copper**
**Jaw**

_**Cross section at shower max.**_

**Copper**

**Fracture temp. of copper **
**      ****is about 200 deg C**

- What is the damage area in a missteering accident?

**Assumed Damage threshold seems inconsistent with FNAL experience**

## FY2005 Deliverables

- Collimator Assembly & Test Area (SLAC-ESB)

- RC1 CDR Draft
- 9/30/05
- 32 pages + figures

## FY2006 Work PlanNon-beam Mechanical & Thermal Performance of RC1

- Single jaw thermal test: one jaw with internal helical cooling channels to be thermally loaded for testing the cooling effectiveness and measuring thermal deformations.
- Heating by commercial electric resistance heaters coupled to the jaw with thermal grease
- Operated in a tank purged with inert gas to protect the copper jaw from oxidation.
- Flexible cooling supply that won’t be intended to allow rotation of the jaw.
- A FE model of the test jaw will be used as a benchmark to evaluate the response of the test jaw to the test conditions.
- Full RC1 prototype: a working prototype for bench top testing of the jaw positioning mechanism, supported to simulate operation in all necessary orientations, but not intended for mounting on actual beamline supports with actual beamline, cooling, control and instrumentation connections.
- Lidded vacuum tank for easy access.
- Cooling water feed-throughs and flexible connections as realistic as possible.
- A reasonable effort will be made to test RC1 under heat loading but this will probably prove to be impractical.

## FY 2006 Deliverables

- Final version of RC1 CDR
- Nov. 1, 2005 ?
- External review of RC1 CDR
- Nov. 14-18, 2005 ?
- Dec 12-17, 2005 ?
- Performance report on RC1
- Sept.30, 2006

## FY2006 Staffing

- Expect continued involvement of existing collaborators at current level
- Devoted engineer
- negotiations with SLAC “Klystron” shop underway
- negotiations with SLAC “Research Division” ME “shop” underway
- employment requirements prepared & will be sent to:
- Fermilab, CERN, etc.
- Mercury News, etc.
- Devoted postdoc
- Advertisement prepared
- People coming through for a “SLAC Postdoc” interviewed
- In-house & external shop & design work as needed

## Detailed FY2006 Work Plan

## Inter-Lab Collaboration

- Excellent good will & cooperation limited only by busy work loads on other systems
- Exchange of mechanical drawing files
- Installation of latest FLUKA at SLAC
- Transfer of latest mod to SixTrack
- Latest hit maps with 60cm primaries
- Invaluable 3 day visit by 4 CERN staff
- Monthly video meetings mostly killed April-present due to visit, other meetings, summer, ...
- Next video meeting Oct 11, 2005
- CERN review of SLAC draft CDR
- CERN participation in RC1 CDR review
- Exchange of detailed technical information will be crucial to delivering prototypes on time
- Drawing of support structures for H, V Skew
- Ideally, CERN would send old prototype parts (i.e. everything [support structure with steppers, motors, bellows, LVDTs,...] except for the tank & cylinder jaws) rather than have SLAC re-fab from drawings or from transcriptions of drawings

## Conclusion

- To meet the Jan.1, 2008 RC2 ship date requirement SLAC and CERN collaborators have agreed on an initial set of specifications for the first mechanical prototype RC1
- based on extensive but incomplete studies done to date
- consistent with CERN beam & mechanical constraints & which uses Phase I design to maximum extent
- RC1 Prototype Conceptual Design, while not 100% complete, has been written up and serves as a start point for construction.
- report to be finalized & reviewed in FY2006
- Fabrication of RC1 in two main steps in FY2006, with appropriate thermal mechanical tests, should validate most of the design issues
- Design extension to RC2, a beam-test-capable prototype, will occur in parallel
- Good (but of course could always be better) communication and exchange of information marks collaboration between labs
- 100% devoted manpower required to ensure success

## Status of Phase II Efficiency Studies

- Excellent understanding of the code:
- Tracking simulations of 1m metal secondary collimators at 7 show inadequate efficiency (plot shown previously)
- CERN provided upgraded code with absorbers & tertiary collimators added will hopefully show adequate performance
- Continue to understand playoff between gaps, lengths and materials and provide loss maps for use as FLUKA input for suggested modifications

## Vertical & Skew Collimators 

**Secondary halo in normalized**
**phase space at the end of**
**collimation system**

**Collimators are projected to **
**The end of collimation system**

**Primary**
**collimator**

**This is an independent check of the simulation code, since the collimators are plotted**
**according to the lattice functions calculated using MAD.**

**6 and 7 sigma contours**

## Tertiary Halo: Particles Escaped from the Secondary Collimators

**TCSG.D4L7.B1**

**TCSG.E5R7.B1: last skew collimator**

**Number of particles beyond**
**10******** is 73, which is consistent**
**with the efficiency calculation:**
**73/144446 = ****5x10****-4****.**
**Tertiary halo at large amplitude**
**is generated by the large-angle**
**Coulomb scattering in the last**
**collimator.**
**If we add a tertiary collimator**
**at 8******** in the same phase as**
**the collimator: TCSG.D4L7.B1**
**after the secondary collimators,**
**the efficiency should be better**
**than ****1x10****-4****.**

## Status of Phase II Energy Loss Studies

- FLUKA with “simple” CERN-provided input file modeling ~40m around primary collimators used for all SLAC studies
- Let “pencil beam” halo interact in primary vertical carbon collimator and study energy deposition in rectangular 25x80mm jaws at 10
- Assume 80% inelastic int. in primary, 2.5% in each jaw of secondary
- Vary jaw material & provide energy deposition grid on jaw to ANSYS
- 2.5mm x 8mm x 5cm rectangular grid, mapped onto cylinder
- Understand secondary particle content, energy & spatial distributions
- Use CERN provided loss maps for H,V,Skew halo with jaws at 7 and re-calculate energy deposition grids
- Study accident case:
- Transverse extent of damaged region
- Longer term goal of upgrading to current CERN input structure with much richer description of all devices in tunnel
- For the moment, ask CERN for estimates of load on “easier” collimators