First results of BBA testsat FERMI @ Elettra (Trieste)

and

Update from ATF2

Andrea Latina for the CLIC Beam Physics team

Inputs on ATF2 from Juergen Pfingstner and Marcin Patecki

CLIC Project Meeting – June 13, 2014

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Introduction / Disclaimer

• We tested our BBA tools developed for FACET at Fermi, Elettra, Trieste

• Due to some bugs in the software interfacing our tools with their control system, we ended up having only three hours of effective beamtime

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Fermi @ ElettraFree Electron Laser for Multidisciplinary Investigations

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FERMI electron beamlines

Single-pass FEL w/ 10 Hz repetition rateLinac energy: from 100 MeV to ~1.2 GeVBunch charge: 800 pCBunch length: from 1.5 mm to 60 micron Emittance at gun: ~1.2 mm mrad

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The Fermi control room

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BBA setup and System IdentificationThe goal was to test our automatic steering tools:- Orbit + Dispersion + Wakefield

correction(1:1 + DFS + WFS)

BBA Setup:• 27 X correctors• 27 Y correctors• 30 BPMs

Machine:• 1.5 betatron oscillations• Effective bpm resolution = 5 - 10 micron• Single-bunch 10 Hz repetition rate• SysID time required:

– About 3 minutes to measure 1 response matrix (can be reduced to 30 seconds, with deeper integration in their control system)

Measured horizontal orbit response matrix

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Dispersion-Free Steering

The dispersion was measured reducing the amplitude of klystron 2 to 98% of its nominal value

This operation occurs in 1 cycle @ 10 Hz

Weight for DFS = 7 (tuned for ~10 micron BPM resolution)

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800 mm

200 mm

Dispersion measurement before DFS

9Vertical dispersion reduced by a factor ~40 ! Horizontal dispersion by factor ~4 (!)

25 mm

50 mm

Dispersion measurement after DFS

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Emittance before BBAat the end of L4

HV

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Emittance measurement after DFS

Horizontal emittance from 4.31 mm mrad to 3.30 mm mrad. Vertical emittance wasn’t good though: needs investigation.

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1:1 + WFS

The wakefields were measured by changing the bunch charge to 650 pC(tests with 900 pC were foreseen, but there was not time for performing them)

Changing the charge takes about 10 seconds (time for charge feedback to converge)

Weight for WFS = 7 - 20 (tuned for ~10 micron BPM resolution)

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1:1 + DFS + WFS

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Emittance measurement after1:1 + DFS + WFS

HV

Emittance summary at Linac End: (H; V) (measurement error: ~±0.05 mm mrad)

Before correction: (4.31; 3.21) mm mradAfter DFS: (3.30; - ) mm mradAfter DFS+WFS: (2.75; 2.57) mm mrad (-35% in X, -20% in Y)

Ground motion correlation experiment at ATF2

Acquisition of • BPM readings

Acquisition of• GM readings• Beam arrival signal

• Goal 1: Show that the beam motion (due to ground motion) can be predicted via motion

sensors (correlation between two measurements).

• Goal 2: Correct the beam motion via a feed-forward system.

• Purpose: Such a feed-forward system could simplify and improve the ground motion

mitigation for ATF2 and for linear colliders in general.

• Experimental setup for goal 1:

J. Pfingstner & M. Patecki

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Region with strong ground motion source

1.Water pipes under girder

(probably touching at one point)

2.Heavy objects on the girder (lead

bricks, Dipole magnet). This could

lower resonance frequency.

Q1X

Q2X

Cooling water pipes

At least two were problems identified

J. Pfingstner & M. Patecki

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Orbit jitter reduction after detecting excitation sources

Beam jitter

• The correlation between motion sensors and BPM measurements have been up to 70%.

• Strong excitation of quadrupole motion was detected via motion sensors.

• An inspection showed that water cooling pipes and tubes were touching the girder.

• After removing the excitation, orbit jitter was reduced from 20% to 14% (half the power).

• Similar excitation detected and removed further upstream. Later measurements revealed the existence of another jitter source. This has to be

investigated.

Correlation

J. Pfingstner & M. Patecki

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Conclusions / Future PlansI. Beam-based alignment tests• Fermi is a very good machine for tests

– Very fast control system– Excellent diagnostics

• Our tools worked very well: emittance reduced by ~35% in H and ~20% in V

• Future plans: near future– Study convergence and fully explore the space of parameters– Envisage tests of tuning bumps? on-line parasitic DFS / WFS?

II. Ground-motion correlation experiment at ATF2:• Important progress:

– One jitter source located and removed: orbit jitter was reduced from 20% to 14% (half the power)

– Correlation measurements improved as well

• Future plans:– Search for the remaining jitter sources, by putting the sensors to further locations– Start preparing for goal 2 (uncertain time scale)

III. Other tests: FACET, Wakefields in the accelerating structures, …