# Presentation: 108885

## Accelerator Physics & Beam Commissioning

_**US LHC Accelerator Research Program**_

_**Accelerator Physics & Beam Commissioning**_

- With vital contributions from W. Fischer,
- M. Furman, T. Markiewicz, F. Pilat, T. Sen, ......

**What are the DRAFT plans for FY04 (and FY05)?**
**(How sensible will these lists look in 12 months time?)**

## Accelerator Systems “BASELINE” budget

## Instrumentation – “baseline is prolog”

**Instrumentation – “baseline is prolog”**

## 1) Tune and Chromaticity Feedback

- Need to establish “Task Sheets”
**1) Tune and Chromaticity Feedback**
- 	- separate studies at BNL & FNAL for 2 years, then make
- 	  a technology choice
- 	- multiple oscillators?
- 	- control room cognoscenti assert that this will be a critical
- 		commissioning and (early) operational tool ...

**Initial Instrumentation**

## Pilot bunch: 5·109 p [P. Collier, Chamonix XII] 

- Allowable loss at injection or snapback: 5·1010 p [10 times loss allowance at store]
- No chromaticity feedback: chromaticity snapback may be ~20 units (non-reproducible 20% part of ~100 units)
-  ~20 leads to ~10% beam loss [~Tevatron experience]
-  100 pilot bunches can be accelerated through snapback, or 5 nominal bunches
****** ****Luminosity ~   ****10****31**** cm****-2****s****-1 **(5 nominal bunches/ring)****** ****Luminosity ~5****·10****29**** cm****-2****s****-1 **(100 pilot bunches)**  **

**How much lumi without chromaticity feedback?**(W. Fischer)                              _Very rough estimate_

## 2) Luminosity Monitor

**2) Luminosity Monitor**
- 	- build eight 4-channel devices in FY2005-2006
- 	- 40 Mhz demonstration is essential in FY04, eg
- 	  for technology choice (CdTe)
- 	- evaluate compatibility with ZDC lumimonitors

**Initial Instrumentation**

## Initial Instrumentation

**3) Longitudinal Density Monitor**_**ing**_
**	****1) Abort Gap Monitor**
- 		- simple, robust, dedicated, reliable
- 		- critical (even early) for Machine Protection System
- 	**2) Optical Sampling System**
- 		- very powerful and sexy as a tool to study longitudinal 		  beam dynamics, eg tomography, diffusion, ...
- 		- state-of-the-art, complex, multi-purpose
- Are these 2 devices “one and the same”?
- Review by Machine Protection Committee?

## Beam Commissioning

- TI8 test with beam		Sept	2004 !
- Commissioning sector 7-8	May	2005
- Injection test with beam	April	2006
- TI2 commissioning		April	2007
- LHC commissioning		April	2007 ->

- Consistent with this schedule – NOW (FY04) - establish
- WHAT “1 US physicist on every control room shift” means, and
- HOW to do it ....

## Commissioning – topics

- What we can offer in the transfer line and injection beam tests?
- If LARP becomes responsible for a problem/topic, we must have the resources and committments to do so.  It would be a failure if CERN took over a problem assigned to LARP.
- With CERN, establish which commissioning problems are sufficiently covered, and which are not.
- Avoid covering a problem twice, or not covering it at all!

**Commissioning – topics**

## Commissioning – people

- Responsibilities will be quite different from person to person.
- Some (eg those intimately involved in instrumentation development) have a natural project, others may not.
- Define one or more principal CERN contacts (cf Oliver Bruning)
- Maybe one contact for all of us, or one for each of us, or one for some of us and ....

**Commissioning – people**

## Commissioning – controls

-   control system”
- 	- to allow remote collaboration
- 	- make LHC data/database available in real time
- 	- define LARP analysis and applications
- Suggest tools that are vital at other machines
- 	- sequencer, ramp management, on-line modeling, 			  databasing, LogView, SDA, ...
- Questions of firewalls and bandwidth have to be addressed.
- Remote Operation test beam experiments at RHIC & FNAL?

**Commissioning – controls**

## Commissioning

- Hadron Collider Commissioning Workshop (in early discussions)
- 	- LARP “is a stakeholder” in any scenario, but
- 	- the broader the workshop scope, the less useful it will be

**Commissioning**

## Interaction regions – optics

- Feasibility of upgrade options with divergent axes quadrupoles
- Prioritize upgrade scenarios on the basis of known LHC limitations (dispersion suppression, matching section)
- Determine minimum space needed between IR separation dipoles (input needed from Magnet program)
- Determine minumum space needed between IR quadrupoles with parallel axes (input from Magnet)
- Defer field quality requirement discussion for IR options to 2005+
- Need an IR Optics workshop?

## Interaction regions – correction

**Interaction regions – correction**

- Conceptual design for different IR upgrade options
- Develop operational IR correction techniques (pre-upgrade)
- Non-linear correction system testing at RHIC
- Test driving term compensation scheme for LHC IR corrections (as implemented in an LHC simulation package)
- Test of  beta star tuning knobs developed at CERN for the LHC.
- RHIC beam experiment?
- Measurement techniques for non-linear and skew chromaticity,
- dynamic aperture (BNL, FNAL)

## Electron cloud

**SPS simulations**
-   	- reproduce measured electron energy spectrum & spatial
- 	  distribution
- 	- reproduce calorimeter results
- 	- POSINST vs ECLOUD: understand and iron out
- 		differences
- 	- Calibrate MAP method for electron cloud density and
- 		flux (BNL)
- Obtain better data for **secondary emission yield and emission **
**spectrum for actual beam screen samples**
- 	- Desirable to reach Eo < 20eV (important and hard
- 		to measure)

## Electron cloud

- Simulate the **effects of EC on beam**
- Assess EC density **diagnostics using microwaves** (?)

**Electron cloud**

## Beam-Beam

- Bench-mark and validate strong-strong codes
- Beam-beam compensation with electron lens and possibly wires
- Coherent mode observation and suppression - crossing angles?
- Measurement of beam-beam resonance driving terms
- Effect of bunch length and crossing angles on 1) lifetime 2) background, 3) tunes, 4) sweeping lumimonitor
- Emittance growth, background, stability of collisions with transverse offsets

## Energy deposition and collimation

- Study magnet designs for different upgrade IR layouts
- Study performance of LHC machine protection system
- Material damage testing for phase 1 LHC collimators? (SLAC)
- Measure short and long range wakefields of Phase I collimators? (SLAC)

## Consumable Collimators

- SLAC has developed a consumable collimator for the NLC collimation system, allowing a finite number of damage events before the collimator needs to be replaced.
- The nominal LHC Phase I system is not expected to survive Phase II abort kicker misfires (25 ns bunch spacing, L = 1e34).
- A modified NLC consumable collimator probably would survive
- An R&D project could deliver a tested prototype and drawing package by the end of 2007.
- This project seems to be a natural fit to the LARP

## Acknowledgements

**Sincere thanks to all the participants, plus**
- 	David McChesney
- 	Diana Votruba
- 	Ila Campbell
- 	Mary Campbell
- 	Linda Roberts &
- 	     the Danfords staff

## Slide 21