# Presentation: 132800

## CollimationClosing RemarksTom MarkiewiczSLAC

- 21 October 2004

***bnl - fnal- lbnl - slac***

_**US LHC Accelerator Research Program**_

## Agenda

## Building an LHC collimator

- Vacuum tank with two jaws installed

- Beam passage for small collimator gap with RF contacts for guiding image currents

## Mechanical movement and tolerances

- Collimators moved in a FULLY operational way:
- Closest gap of ~ 1 mm achieved with circulating beam! Mechanical tolerances and angular alignment at the ~ 100 m level!
- 	 	Much smaller gaps than required in the 7 TeV LHC have been 	achieved with the LHC collimator prototype and circulating beam!
- 		Gap known to 100 m with excellent reproducibility (20 m) over 16 h 	(motor setting reproducibility)!

- Gap width

- Gap center

## Precision set-up

- LHC requirement:	Center gap around beam with ~ 25 m 					accuracy (beam-based alignment).
- SPS beam:		120 h beam lifetime			orbit stable to 5 m			 ideal tuning conditions
- Observation:		Beam-based alignment ... 		**... to 100 ********m is OK!****	****	****	****	****... to 50 ********m is difficult!****	****	****	****	****	****	****... to 10-20 ********m is impossible?**

- Beam distribution close to the edge after 30s

## Collimator MDs #2 – (some) BBQ results

- Collimator cycled between
- 51 mm and 3.86 mm (5h04)
- 51 mm and 2.86 mm (5h35)
- 51 mm and 2.46 mm (5h43)
- 51 mm and 2.06 mm (5h50)
- 51 mm and 1.86 mm (5h58)

## Collimator MDs #2 – (some) BBQ results

## Impedance expectation and measurement in SPS

*Preliminary Collective Effects Team*

## Present effort at CERN

**Continue phase 1 work** (additional collimator design types  absorbers).
**Finalize beam tests**. Very encouraging preliminary results confirm our assumptions on phase 1.
**Produce** phase 1 collimators and absorbers. Orders for all components between December 04 and March 05: European industry and/or Novosibirsk.
- Understand how to **make phase 1 collimation work**** **(involves accelerator physics and operational studies)
- Understand **general limitations** for collimators in LHC environment (radiation damage, reliability, ...)
- Prepare infrastructure

## Look beyond phase 1

**CERN resources at present very busy with phase 1 collimation**.
- Preliminary beam results support **need for phase 2 collimators**!
**Need to start preparing phase 2**** **as early as possible in order to use available time for R&D on advanced solution. Radiation will impose limits for latest possible installation!
- LARP plays crucial role in pushing ahead now!
- CERN should put some resources for phase 2 R&D on alternative paths later next year!
- Ideal scenario: **2-3 different phase 2 technologies**** **available for beam tests 3-6 months after first beam in LHC.
**Decision on phase 2** based on experience with phase 1 collimators and phase 2 prototypes ~ 1.5 years after first beam in LHC.

## BNL Summary

- BNL collaborating with the LHC collimation WG: colltrack code is installed and compiled at BNL
- There is a need for code benchmarking and comparison in the world of loss maps
- data will be analyzed with the help of the LHC collimation WG (grad. student for 1-2 months)
- Multiple collimator steering will likely require some beam time at RHIC
- Hiring process of LARP postdoc started (likely for both fields, collimation and EC)

## Compare RHIC data with simulation

- Ray Fliller

- Fill 4854
- 2-stage
- (axis swapped!)

- Fill 3254
- 1-stage

- Needs some more work!

## Yunhai’s Benchmark Run of SIXTRACK to Ralph’s Simulation of Phase I Collimation System 

- Injection energy: 450 Gev

- # impacts

- # absorbed

- <impact parameter>

- spread of impact
- parameter

## Efficiency vs. Length

- Ralph’s phase II              Yunhai’s phase I

- Injection energy: 450 Gev?

## Efficiency vs. Length at Collision Energy (7 Tev)

**only phase I collimators are used in simulation**

## Examples of Fermilab Energy Depositions Studies

## Fermilab LARP ENERGY DEPOSITION: FY05

- MARS15 and MAD-STRUCT-MARS developments.
- 2. Refining models for operational and accidental beam loss.
- 3. Modeling in IP5 and CMS with tertiary collimators.
- 4. Modeling of energy deposition in Phase 2 collimators
- 5. Uncertainty analysis.
- 6. Possible radiation tests of collimator materials (BNL, FNAL, MSU).

## Energy Deposition in Metal Phase II Secondary Collimators w/ Carbon Phase I Collimators Open

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

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

## Steady State Temperature of TCSH1 at shower max when jaw at 10 is in contact with 20°C H2O and 80% (5%) of 90kW of primary beam interacts in TCPV (TCSH1)

- Steady State Temperature of TCSH1 at shower max when jaw at 10 is in contact with 20°C H2O and 80% (5%) of 90kW of primary beam interacts in TCPV (TCSH1)

- 25mm

- 80mm

- Boundary Condition: Convection CoefficientHCH20=11880 W/m2/°C

- CV  Cu taken as constant

- Jaw: 25x80mm Solid Cu PTOT=1270W

- Power Density to H2O
- 0.38 MW/m2(H2O boils at 1 atm @ 1.3E6)

- Doyle: 2004-09-28

## Time Dependence of Peak Temperature  of TCSH1 shower max when jaw at 10 is in contact with 20°C H2O and 80% (5%) of 450kW of primary beam interacts in TCPV (TCSH1)

- Time Dependence of Peak Temperature  of TCSH1 shower max when jaw at 10 is in contact with 20°C H2O and 80% (5%) of 450kW of primary beam interacts in TCPV (TCSH1)

- Jaw: 25x80mm Solid Cu PTOT=6400W

- Doyle: 2004-09-28

- Beam Side of Jaw

- Water Side of Jaw

- 10 sec

##  3D Calc of Temperature @ 10 sec of TCSH1 at shower max when jaw at 10  is in contact with 20°C H2O and 80% (5%) of 450kW of primary beam interacts in TCPV (TCSH1)

-  3D Calc of Temperature @ 10 sec of TCSH1 at shower max when jaw at 10  is in contact with 20°C H2O and 80% (5%) of 450kW of primary beam interacts in TCPV (TCSH1)

- Jaw: 25x80mm Solid Cu

- Power Density to H2O
- 1.2 MW/m2(H2O boils at 1 atm @ 1.3E6)

- Doyle: 2004-09-28

- Boundary Condition: Convection CoefficientHCH20=11880 W/m2/°C

- CV  Cu taken as constant

- Viewed from beam side

## Materials Study at 450 kW loss rate after 10 sec.

- Same caveats as specified in previous slide

- 25mm thick Cu and W have Temperature above fracture limit and would require pressurized cooling system

## Materials Study at 450 kW loss rate - Steady State

- Same caveats as specified in previous slides

- Although NOT a strict requirement as specification calls for beam dump after 10 sec:25mm thick Ti and 5/20mm Cu/Be have Temperature above fracture limit; Ti would require pressurized cooling system

## Steady State Cooling Estimate for 90kW loss rate

## Conclusions

- At our current level of understanding
- Thin Cu,	10 kW
- Al,	  7 kW
- Be,	  1 kW
- Collimators seem feasible.  Total power needs to be scaled by
- +10%	Non-Jaw part of collimator
- +25%	Gap at 7 sigma
- Small%	Changes in loss map
- -~25%	If length reduced
- +25%	Margin + more sophisticated calculations
- Al and thin Cu not too dissimilar from CERN Phase I Carbon (6kW +1kW)
- Be seems “easy”-need to understand limitations
- Can we design 10kW in rotating geometry? Can we meet space constraints?
- Will material maintain mechanical tolerances when loss rate goes to 450 kW?

## Last Remarks

- Agreement for monthly LARP-CERN “Phase II Collimators” video or phone meeting the first Thursday of month 17:00 CET / 8:00 PST / 10:00 CST / 11:00 EST
- Agreement on roles of participating institutions
- Task List re-re-write Friday 10/22
- Informal answering of many questions
- General agreement on transfer of codes
- Discussion of relevant status reports & decision points
- Worthwhile meeting!