Beam Delivery System: status and plans of R&D until CDR R. Tom - - PowerPoint PPT Presentation

Beam Delivery System: status and plans of R&D until CDR

• R. Tom´

as, D. Angal-Kalinin, B. Dalena,

• L. Fernandez, F

. Jackson, J. Resta, G. Rumolo,

• A. Seryi, P

. Schuler and D. Schulte CLIC ACE 2009

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.1/23

Contents

• New instrumentation: The polarimeter
• Preservation of emittances:
• Transport aberrations
• Failure to tune the FFS
• .
• ATF2
• Collective effects

   Resistive wall Fast ion instability Collimator wakefields

• Machine protection:
• Collimation systemm
• Plans towards CDR

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.2/23

Contents

• New instrumentation: The polarimeter
• Preservation of emittances:
• Transport aberrations
• Failure to tune the FFS
• ′′
• ATF2
• Collective effects

   Resistive wall Fast ion instability Collimator wakefields

• Machine protection:
• Collimation systemm
• Plans towards CDR

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.2/23

Contents

• New instrumentation: The polarimeter
• Preservation of emittances:
• Transport aberrations
• Failure to tune the FFS
• ′′
• ATF2
• Collective effects

   Resistive wall Fast ion instability Collimator wakefields

• Machine protection:
• Collimation systemm
• Plans towards CDR

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.2/23

The BDS

100 200 300 400 500 600 0.5 1 1.5 2 2.5 3

• 0.05

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 β1/2 [m1/2] D [m] Longitudinal location [km] Diagnostics Energy collimation Transverse collimation Final Focus system βx

1/2

βy

1/2

Dx

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.3/23

Polarimeter location & performance

• 2
• 1.5
• 1
• 0.5

0.5 500 1000 1500 2000 2500 3000 x[m] Longitudinal location [m] BDS layout IP directions (0.6mrad)

Laser IP at 742 m and detector at 907 m. Relative polarization measurement error is 0.61% (for 1s).

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.4/23

BDS emittance “spoilers” by design

• CLIC BDS transport aberrations have been

extensively minimized (MAPCLASS, extra non-linear elements, etc)

• Aberrations increase vertical IP beam size by

15%

• Synchrotron radiation reduces luminosity by

20%

• (in ILC these effects are below the 1%)

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.5/23

Vertical IP beam sizes and chromaticities

Project Status σ∗

y [nm]

ξy FFTB Measured 70 17000 ATF2 Commissioning 37 19000 ILC Design 6 15000 ILC low power Proposed 4 30000 CLIC Design 1 63000 CLIC, the most challenging.

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.6/23

Imperfections as emittance “spoilers”

• 10µm transverse misalignments can

decrease lumi by 10−6

• 10−5 relative gradient error in QD0

decreases lumi by 0.94

• Tuning algorithms are fundamental!
• Can we tune the FFS using the Simplex to

maximize lumi?

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.7/23

Current status of FFS tuning

2 4 6 8 10 12 14 0.6 0.8 1 1.2 Counts Relative final luminosity [L0]

Pre-alignment is 10µm 80% of the cases reach 80% of the lumi in 18000 iterations.

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.8/23

How to improve tuning performance?

• Use of more clever algorithms than the

Simplex (presently on-going)

• Tune in a beta-squeeze sequence (like

colliders)

• Relax the optics
• Andrei Seryi proposed a new optics with

double L* to ease QD0 stabilization, let’s see what happens

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.9/23

Comparing Andrei’s FFS to CLIC nominal

100 200 300 400 500 600 700 800 900 100 200 300 400 500 600 700 800 βy [km] Longitudinal location [m] Andrei’s proposal CLIC nominal

Andrei’s prop: L*=8.0m, β∗

y=0.10mm

CLIC nominal: L*=3.5m, β∗

y=0.07mm

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.10/23

Sensitivity to misalignments

10-12 10-10 10-8 10-6 10-4 10-2 100 2 4 6 8 10 Relative luminosity (L/L0) Transverse misalignments (σx,y) [µm] L*=3.5m L*=8.0m

Doubling L* increases sensitivity to misalign- ments by a factor of 4

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.11/23

Sensitivity to QD0 gradient error

0.9 0.92 0.94 0.96 0.98 1 1.02

• 0.15
• 0.1
• 0.05

0.05 0.1 0.15 Luminosity (L/L0) QD0 relative gradient error [10-4] 0.05 0.03 L*=8.0m L*=3.5m fits

Doubling L* increases sensitivity to gradient error by a factor of 2

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.12/23

QD0 specifications

L*=3.5m L*=8.0m Gradient 575T/m 211T/m Aperture (radius) 3.5mm 8.5mm Outer radius 35mm 70mm QD0 jitter 0.15nm 0.18nm QD0 support detector ground QD0 technology PM PM QD0 grad tol. 5×10−6 3×10−6 A superconducting QD0 adds the extra challenge

• f stabilizing coils.

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.13/23

Tuning longer L* with better pre-alignment

2 4 6 8 10 12 14 16 18 0.5 0.6 0.7 0.8 0.9 1 Counts Relative final luminosity L/L0

Pre-alignment is 2µm Same tuning performance as for nominal by re- ducing pre-alignment a factor 5

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.14/23

ATF2 ultra-low β proposal

• CARE/ELAN-2008-002 proposed a squeeze
• f the ATF2 IP β-functions by a factor of 4
• σy ≈20 nm, ξy ≈76000
• ATF2 ultra-low β will experimentally prove

CLIC-like aberrations and tuning algorithms.

• Beneficial for the ILC project, more in

particular for the ILC low power option.

• This proposal was accepted
• Presently a CERN PhD working on this

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.15/23

Collective effects: Resistive wall

• 25
• 20
• 15
• 10
• 5

5 10 15 20 25 0.5 1 1.5 2 2.5 3 Last bunch vertical excursion [µm] Longitudinal location [km] Resistive wall effect (Cu beam pipe) Initial batch offset=0.2µm radius=2mm radius=3mm radius=4mm radius=6mm

8mm Cu beam-pipe is enough to neglect resistive

• wall. Only QD0 has a smaller aperture.

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.16/23

Collective effects: Fast ion

Two sources:

• Scattering ionization
• Field ionization

10 nTorr seem enough to avoid fast ion instabili- ties.

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.17/23

Collective effects: Collimator wakefields

5 10 15 20 25 0.05 0.1 0.15 0.2 0.25 ∆L/L0 coll wakefield no coll wakefield

10σx,44σy Assuming an initial jitter of 0.2σ wakefields peak lumi reduction is 20%. Open the collimator gaps?

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.18/23

Energy collimator (Be) survivability

50 100 150 200 250 300 350 50 100 150 200 250 300 350 400 450 500 550 Distance [mm] Temperature increment [K] Temperature increment in a Be spoiler with tapers and a 0.5 rad. lengths body hit by a full CLIC train

Temperature raise after impact of a full train below melting level. (different philosophy than ILC)

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.19/23

Collimator gap scan

x

σ N

10 20 30 40 50 60

y

σ N

20 40 60 80 100

a

x

σ N

10 20 30 40 50 60

y

σ N

20 40 60 80 100

b

Good particles for QF1 and QD0 Bad particles for QF1 or QD0

x

σ N

10 20 30 40 50 60

y

σ N

20 40 60 80 100

c

x

σ N

10 20 30 40 50 60

y

σ N

20 40 60 80 100

d

x

σ N

10 20 30 40 50 60

y

σ N

20 40 60 80 100

e

x

σ N

10 20 30 40 50 60

y

σ N

20 40 60 80 100

f

Acceptable collimation depths are between 10- 15σx and 44-55σy.

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.20/23

Plans towards CDR

• CLIC 500 GeV lattice optimization (new

CERN student on August)

• New tuning algorithms and knobs (help from

SLAC, LAL, ATF2...)

• ATF2 ultra-low β progress (new CERN PhD

since March and ILC)

• Review and optimization of collimation:
• wakefields with new parameters (UK)
• simulations including secondaries (UK)
• QD0 review (Detlef)
• Global feedback studies (new CERN fellow

since May)

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.21/23

Some bonus points

• Luminosity measurement, fast and precise

(?)

• Crab cavity phase specifications review

(0.025◦ for 12 GHz) (A. Dexter ?)

• Post-IP polarization measurement (help from

ILC?)

• 15mW beam dump (help from ILC?)

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.22/23

Stabilization to the 0.13nm

Ground isolation and resonance rejection works.

Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.23/23