# Presentation: 183787

## Wire Compensation

- SPS wire experiment – July 2004
- Tevatron wire compensation studies
- Wire compensation proposal in LARP
-  Road map for an IR upgrade

- Tanaji Sen
-    FNAL

- LARP Meeting at Napa

- October 19, 2004

## New Wires installed in 2004

- 3 wires (60cm long) in each unit
- Only bottom wire was powered
- Beam pipe on vertically movable
-  stands (movable by 5mm)

- LARP Meeting at Napa

- October 19, 2004

## SPS beam conditions

- Energy = 26 GeV
- Intensity ~ 4E12 in 12 bunches
- SPS cycle 4.5 seconds
- Wire excitation
-     - powered on at 0.5 secs
-     - full current at 1.0 secs
-             (max current = 270A)
-     - ramped down at 4.0 secs
- Orbit changes and tune shifts due to wire
-     were compensated.

- LARP Meeting at Napa

- October 19, 2004

## Position sensitivity:prediction & measurement

- BBSIM: No compensation beyond ~3mm
- Measurement: Compensation lost beyond ~2.5mm from optimum

- LARP Meeting at Napa

- October 19, 2004

## SPS wire compensation

- Intensity Loss compensated
- By 2nd wire

- Emittance shaving occurs early

- LARP Meeting at Napa

- October 19, 2004

## SPS experiment – tune scan

*30.07.04*

- nearly perfect
- compensation

-                ?

- tune scan with compensation
- of 2 BBLRs in the CERN SPS
- near the LHC working point

*no BBLR*

*compensation*

*1 BBLR*

*path in the tune diagram*

- F. Zimmermann

- LARP Meeting at Napa

- October 19, 2004

## Tevatron wire compensation study

-  Compensation at injection
-  Compensation at collision
-        Local compensation of  parasitics
-        Non-local compensation of parasitics
-        Wires with elliptic cross-section
-        Multiple wires

- LARP Meeting at Napa

- October 19, 2004

## Beam separations in the Tevatron

- Experiments at B0 and D0

- Beam separations at parasitics
-  around B0 and D0 are ~ 5sigma
- Beta functions are large in one plane
-  – beams are very elliptical at these
- locations

- LARP Meeting at Napa

- October 19, 2004

## Contributions of parasitics

- Parasitics around B0 and D0
-  contribute largest tune shifts

- Several parasitics around the
-  ring cause comparable
-  diffusion

- LARP Meeting at Napa

- October 19, 2004

## Fields of round & elliptical beams 

- Difference in kicks between
-  a round beam and a wire.
- Less than 1% beyond 3 sigma

- Difference between elliptical
-  beams and a wire.

- Round

- LARP Meeting at Napa

- October 19, 2004

## Non-local compensation

- Conditions for
-  compensation of 1
-  beam-beam kick

- Compensation of several beam-
-  beam kicks by a wire can only
-  be done in an average sense.

- LARP Meeting at Napa

- October 19, 2004

## Local & non-local compensation

- Round beams at 9 sigma
- Wire reduces diffusion

- Compensation of parasitics
-  near B0 and D0. Wires placed
-  at appropriate phase advances.
-  Wires do not help.

- LARP Meeting at Napa

- October 19, 2004

## Elliptical Wires

-  Round wires are not well matched to the field of  very elliptical beams.
-  Wire with elliptical cross-section is better suited.
-  Field of the wire matches that of the beam to better than 2% outside the core.
-  Could be tested in simulations.

- LARP Meeting at Napa

- October 19, 2004

## Multiple Wires

-  Could adapt to changes in helix
-  Field of strong beam could be better matched across width of weak beam
-  Multiple resonances could be compensated
-  Issues
-  Robustness
-  Impact on strong beam
-  .....

- LARP Meeting at Napa

- October 19, 2004

## Wire Compensation Proposal

***Proponents:***
- FNAL: Tanaji Sen, Vladimir Shiltsev
- BNL: Wolfram Fischer
- LBNL: Miguel Furman, Ji Qiang
- CERN:  Jean-Pierre Koutchouk,
-              Jorg Wenninger, Frank Zimmermann

- LARP Meeting at Napa

- October 19, 2004

## Wire compensation proposal

- Experimental demonstration of the principle in the SPS with one wire simulating the beam and the second as the compensator
- Experimental demonstration in a hadron collider (RHIC or Tevatron) or lepton collider (e.g. PEP-II) - *demonstrate use of the  wire for the benefit of this collider, e.g, as scraper, or for future upgrades.*
* ****RHIC - compensation of long-range collisions in eRHIC or after IR upgrades***
*** ******Tevatron - improving performance of  Run-II / BTeV***
- R&D on pulsed wire compensation system; possible test of pulsed wire on beam in existing machine
-  Design of compensation device for LHC assuming success of former points.

- LARP Meeting at Napa

- October 19, 2004

## Wire Compensation in LARP

- SPS  2004, 4  BBLR machine studies generated a lot of data
-      - a partial involvement of a scientist and of a fellow in the analysis
-     -  would benefit from assistance by computer scientists;* *
*    **-  *use as a **test bed for information sharing as a preparation to remote participation in machine studies**; for the sharing of data and analysis procedures and results
- 2) Experimental full-size demonstration:
-       -  which existing collider is most suitable for creating the nominal LHC long-range beam-beam conditions
-       - **refit the SPS devices or build new ones and carry through an**
**     ****experimental study program; **

- 3)  Pulsed wire R&D in collaboration with CERN
-     (typically a few hundred Amperes pulsed at a few MHz or, alternatively,
-     at 40 MHz).
-  LHC implementation: design of  a movable wire compensator suitable for LHC

- LARP Meeting at Napa

- October 19, 2004

## Different IR Layouts

- LARP Meeting at Napa

- October 19, 2004

## IR upgrade – small x-angles

- Dipoles First

- Quads First

- Optics

-          Design
-  cos θ, block coil

-   Energy
- Deposition

-      Wire compensation

- Matching

- Correctors

- Dynamic
- Aperture

- Design Paths

- LARP Meeting at Napa

- October 19, 2004

## IR upgrade: large x-angles

- Design Paths

- Nominal Intensity
-  Crab cavities

-    High Intensity
-  Beam-beam limit

- Superbunches

- ~1500 long
- bunches

- Requires large cavity voltage
-  Emittance blow-up possible

- Huge pile-up
-  May be ruled
-  out by CMS,
-  ATLAS

-  Pile-up still
-   large
-  Intensities
-  may be limited

- LARP Meeting at Napa

- October 19, 2004

## IR upgrade road map for LARP

- Wire compensation

- Quads
-  First

- Matched
- Design

- Correctors
- Field quality

- You are
-  here

- GOAL: Optics design to provide input for Magnet R&D
-               Not to create an optimized design for the LHC

- LARP Meeting at Napa

- October 19, 2004