# Presentation: 215658

## V.Shiltsev: LARPAC advises and Beam-Beam News:* wire compensation at DAFNE* crabbed waist idea

- LARP mtg Wed May 24, 2006

## LARPAC review May 10-12 BNL

- Galayda (chair), Chao, Devred, Minervini, Rode,
- Seryi, Wittenberg, Yamomoto
- L2s and L1s presentations (MAG/AS)
- Charge:
- Strategic goals , incl new tasks
- Progress and milstones
- c)   Management issues
*“**The Committee was impressed with the achievements of the *
*Collaboration in the past 2 years. The LARP research program *
*Demonstrates excellent focus, a strong spirit of cooperation and *
*The clear evidence of synergy within the Collaboration”.*

- LARP mtg Wed May 24, 2006

## Comments:

- Schottky:
- Drawings sent to CERN, should be no problems to be built
- Support complete electronics test in the US labs
- Special care to ensure timing specs met by CERN
- Two trips might not be enough plan for 3
- Need detailed list of milestones upto 1st ramp and 1st beam
- Lumi:
- Design adequate, p and Au tests in RHIC praised
- Rad damage tests a must, _more background studies! _
- Integration OK, more milestones (better planning) for 1st lumi
- Tune FB:
- TCFB success at RHIC, still feed-forward or/and ref.magnet to consider
- Attention to SPS tests, more milestones extending to 1st beam
- Get experience with DAQ software/firmware in the US labs
- GENERAL:
- Provide to CERN list of spare parts
- Prepare written failure and emergency handling
- Use LHC@FNAL for monitoring passive instruments (Lumi, Schottky)

- LARP mtg Wed May 24, 2006

## Comments - 2:

- Commissioning:
- Document details how Instrum experts will continue to be involved in BC
- To select best candidates – need to have a choice- more candidates  lab support  repeat CTF-like attempts to find other possibility
- Toohig Fellows & LHC@FNAL:
- Sluggish LARP response toapplications  streamline it (3 mos !)
- Danger of no people at the room  need appropriate neeting facility (VC $$)
- Phase II collim:
- Hell with RHIC maps , CERN data more relevant and may come firs
- Accel Phys:
- recommend e-cloud collaboration with PEP-1II and ILC DR
- Flux jumps effects may accumulate  consider/analyse diffusion
- Post-commissioning after 2008-09:
- Consider how to sustain LARP participation; set LARP goals
- New initiatives should be consistent with the goals
- New Initiatives :
- Don’t hurt current programs
- Sufficient homework must be invested for each initiative

- LARP mtg Wed May 24, 2006

## DAFNE (Frascati, Italy)

- 1GeV cme e+e- collider
- Peak Lumi 1.5e30
- 110 bunches , 2.7 ns spacing
- 24 parasitic collisions/IP at 8-20 sigma
- Beam-beam tune shift ~0.06
- Crossing angle (hor) 10-15 mrad
-  dL ~15%

- LARP mtg Wed May 24, 2006

## Numerical simulations show that BBLR interactions can be    compensated by current-carrying windings

- Windings OFF

- Windings ON

- Windings ON
- (wrong polarity)

- Particle equilibrium density in the transverse space of normalized betatron amplitude

- (M. Zobov, D. Shatilov)

- Ay/y

- Ax/x

- Ay/y

- Ay/y

- Ax/x

- Ax/x

- LARP mtg Wed May 24, 2006

## Fig. 1 schematic drawing of the current-carrying 

- Fig. 1 schematic drawing of the current-carrying
- wires installation in the KLOE interaction region.

- M.Zobov

- LARP mtg Wed May 24, 2006

## Beam

- Wires

- LARP mtg Wed May 24, 2006

## M.Zobov

- Fig. 3 positron beam lifetime on two time intervals.
- Red hollow dots correspond to wires powered with .9 A
- currents, full blue dots – wires at 3.6 A.

- LARP mtg Wed May 24, 2006

## CRABBED WAIST

- LARP mtg Wed May 24, 2006

##    Crossing angle  geometric luminosity reduction          
+ ( more important ) SB resonances as kick depends on S

- + ( more important ) SB resonances as kick depends on S

**Sz**

**Sx**

****

**z**

**x**

**Sx/******

**Sz*******

**e-**

**e+**

- P.Raimondi

- LARP mtg Wed May 24, 2006

## Crabbed waist
Vertical waist position in z is a function of x:
                        Zy_waist(x)=x/

- _Vertical_ waist position in z is a _function of x_:
-                         Zy_waist(x)=x/

- P.Raimondi

- LARP mtg Wed May 24, 2006

##    Crabbed waist:
   - All components of the beam collide at a minimum betay 
   - The ‘hour glass’ is reduced and the geometric luminosity is higher
   - The bb effect in the section were the beams do overlap is reduced 
   - The bb effect in the sections were the beams do not overlap is greatly reduced
   From tracking, the blowup at the equilibrium goes down to just a factor 2-5  proportional gains in luminosity
sextupole at right phase distance from IP – to be tested in DAFNE (applicable to SuperB)

-    - All components of the beam collide at a minimum betay
-    - The ‘hour glass’ is reduced and the geometric luminosity is higher
-    - The bb effect in the section were the beams do overlap is reduced
-    - The bb effect in the sections were the beams do not overlap is greatly reduced
-    From tracking, the blowup at the equilibrium goes down to just a factor 2-5  proportional gains in luminosity
- sextupole at right phase distance from IP – to be tested in DAFNE (applicable to SuperB)

- LARP mtg Wed May 24, 2006