Transverse feedback: high intensity operation, cleaning, lessons for 2012

Daniel Valuch for the ADT team

The transverse damper system Important role in preservation of the beam’s

transverse emittance

Damping of injection oscillations

Damping of oscillations driven by coupled bunch instability

Within certain limits damping external perturbances

The transverse damper in general The transverse damper is a feedback system: it

measures the bunch oscillations and damps them by fast electrostatic kickers

BPM

BPM Signal Processing

andCorrection calculation

Kicker

Power Amplifier

Ideal equilibrium orbitBeam trajectory

BPM Beam position monitor

Tbeam

Tsignal

Key elements: Beam position

monitor(s) Signal processing

system Power amplifiers Electrostatic kickers Key parameters: Feedback loop gain, phase

and total delay Kick strength System bandwidth The one visible from the

CCC: damping time

LHC transverse damper (ADT)

IP4

beam 2

beam 1

Q7LQ9L Q9RQ7RH.M2.B2H.M1.B2V.M1.B2V.M2.B2

V.M2.B1V.M1.B1H.M1.B1H.M2.B1

beam 2

beam 1

SR4

[V]

[H]

[V]

[H]

[H]

[V]

[H]

[V]

Point 5Point 3 UX451

BPos Q9

BPos Q7

DSPU M1

DSPU M2

BPos Q9

BPos Q7

DSPU M1

DSPU M2

BPos Q9

BPos Q7

DSPU M1

DSPU M2

BPos Q9

BPos Q7

DSPU M1

DSPU M2

SR4

Bpos – Beam Position ModuleDSPU – Digital Signal Processing Unit

ADT as seen from the CCC

PickupBeam

Pos Q7

BeamPos Q9

Pickup

HIGH VOLTAGE SUPPLY

Chirp injection

Level 2

Level 3RF ON

SIGNAL PROC.

CLEANING

Start/StopDampers

SIGNAL PROC.

CLEANING

Start/StopCleaning Power

amplifiers Kickers

Phase advanceNorm. gain

Functions:

Timings:

CCC application:

ADT as seen from the CCC Level1: switches on the heaters, blowers and

control electronics.

Level2: switches on the high voltage power supply, the system is ready for operation. Note: The system contains 16 tetrode amplifiers.

When sitting in Level2 it already consumes more than 0.5 MW of power!

Level3 (RF ON): the power system is fully active and the beam sees any applied excitation: Chirp signals from the BI colleagues. RF signals from the ADT signal processing. Cleaning/blow-up excitation.

ADT as seen by the experts

Sensitive to intensity

Sensitive to tune and bunch spacing

PickupBeam

Pos Q7

BeamPos Q9

Pickup

HIGH VOLTAGE SUPPLY

Chirp injection

SIGNAL PROC.

CLEANING

SIGNAL PROC.

CLEANING

Power amplifiers Kickers

Phase advanceNorm. gain

Setting up: Beam Position Module The Beam Position (BPos) Modules processes the

RF signals from the pickups and calculates an intensity independent, normalized beam position.

Gain of the BPos module must be adapted to the maximum per bunch intensity and expected orbit displacement. Saturation levels are typically set to ~10-20% above

the intended max. intensity with a 2-2.5mm displacement.

Setting up needs to be performed once for each intensity step higher than 10-20%. Setting up for one intensity step takes around 30

min/beam/plane (could be done remotely).

Setting up: Beam Position Module BPos front ends could be damaged by excessive

signals: Injecting nominal when set to pilot/ion settings. Injecting 3e11 when set to nominal settings.

Switching off the ADT from the CCC application does not protect the front-ends from high intensity signals!

In case the ADT is not set-up for given intensity, please ask the ADT experts to “park it” safely.

Setting up: Signal processing unit The Digital Signal Processing Unit (DSPU) collects

data from the BPos modules and calculates the correction kick.

DSPU generates the cleaning signals. DSPU provides data for the injection oscillation

fixed display.

DSPU needs to be set up for different bunch spacings. Currently available settings: 25 ns, 50 ns, 100 ns,

200 ns, >600 ns

Phase advance functions need to be set up when tune changes. Typically 30 minutes/beam/plane plus editing the LSA

functions. (measurement done locally in SR4).

ADT through the cycleGain

Phase shift

Injection probe beam

Injection physics beam

Prepare ramp Ramp

Squeeze

Physics

Abort gapcleaning

Injection gap cleaning

Intensity

Energy

10's turns

100's turns

500's turns

Q injection

Q collisions

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Adjust

Tune feedback

ADT through the cycleGain

Phase shift

Injection probe beam

Injection physics beam

Prepare ramp Ramp

Squeeze

Physics

Abort gapcleaning

Injection gap cleaning

Intensity

Energy

10's turns

100's turns

500's turns

Q injection

Q collisions

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Adjust

Tune feedback

ADT through the cycleGain

Phase shift

Injection probe beam

Injection physics beam

Prepare ramp Ramp

Squeeze

Physics

Abort gapcleaning

Injection gap cleaning

Intensity

Energy

10's turns

100's turns

500's turns

Q injection

Q collisions

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Adjust

Tune feedback

ADT through the cycleGain

Phase shift

Injection probe beam

Injection physics beam

Prepare ramp Ramp

Squeeze

Physics

Abort gapcleaning

Injection gap cleaning

Intensity

Energy

10's turns

100's turns

500's turns

Q injection

Q collisions

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Adjust

Tune feedback

ADT through the cycleGain

Phase shift

Injection probe beam

Injection physics beam

Prepare ramp Ramp

Squeeze

Physics

Abort gapcleaning

Injection gap cleaning

Intensity

Energy

10's turns

100's turns

500's turns

Q injection

Q collisions

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Inje

ctio

n

Adjust

Tune feedback

Injection/Abort gap cleaning In 2011, the injection and abort gap cleaning was

commissioned into routine operation at 450 GeV. The uncaptured beam is cleaned by coherent

excitation until it hits the collimators. Q±0.01 in 15 steps, each 750 turns.

Abort gap cleaning: excitation window fixed in part of the abort gap.

Injection gap cleaning: excitation window slides and covers the next injection slot.

End 2011: Abort gap cleaning commissioned for 3.5 TeV operation. Cleaning strategy being discussed.

Window function

Injection gap cleaning (horizontal plane)Abort gap cleaning (vertical plane)before 1st injection

1st injection

last injection

prepare ramp

before 2nd injection

Cleaningpulse

Sign

als a

cqui

red

durin

g in

ject

ion

of th

e fil

l #18

67

Batch selective blow-up Batch selective excitation using wideband noise

was introduced in 2011. Successfully demonstrated creation of a fully

controlled steady losses on selected bunches as well as emittance blow-up up to the aperture limit

Intention to use ADT for loss maps, aperture measurements, quench tests etc. from 2012 onwards: Needs time for proper commissioning at the 2012

start up. Needs new user applications.

Batch selective blow-up Test from 30.10.2011: A batch of 12 bunches lost

in 4 seconds.

1 sec

1 sec

1 sec

Bunch by bunch observation with ADT25

6k25

6k25

6k25

6k

S magnitude

Internal signal

Bunch position

Radial error

Observation

S I raw

S Q raw

D I raw

D Q raw

Post mortem

256k

256k

256k

256k

Q7 position

Q9 position

Q7 after notch

Q9 after notch

Observation

Q7 position

Q9 position

Q7 after notch

Q9 after notch

Post mortem

256k

256k

256k

256k

Sum after 1-t delay

Sum after activity mask

DAC out

Analogue readback

Sum after 1-t delay

Sum after activity mask

DAC out

Analogue readback

8192

8192

Q7 position

Q9 position

Fixed display

Multiturn applicationgets this buffer

Beam Position module Digital Signal

Processing Unit

Injection oscillationsfixed display

Plans for TS 2011 and 2012 run Recabling of one system:

7/8” coaxial cable damage during the initial installation.

Evaluation of a new type transmission line without corrugation.

last batchno beam

delta signal

Plans for TS 2011 and 2012 run Recabling of one system

Cable damage during the initial installation Evaluation of a new type transmission line without

corrugation

last batchno beam

delta signal

Plans for TS 2011 and 2012 run Detailed study of, and potential improvement to,

the system’s impulse response. Cleaning signals are currently exciting beam out of

the cleaning window. Detailed study of the system noise properties as a

preparation for LS1 and 7 TeV run. Feasibility study for Q measurement using the

ADT data. Residual noise method. Witness bunches method.

ADT gain modulation within turn. Preparation for complete recabling in LS1 (>20km

of 7/8” smooth-wall coaxial cable)

Re-commissioning after the TS Commissioning of the recabled system: 4 hours.

Intensity settings for 1.4 and 1.7e11 ppb: 2x4 hours.

Verification of the loop parameters (phasing, delay): 6 hours.

Commissioning of the blow-up for loss maps: 8 hours (min).

Automatic gain adjustment (pilot/nominal): ?

Re-commissioning after the TS: total 3-4 shifts.

Thank you…