SLS at the Paul Scherrer Institute (PSI), Villigen, Switzerland - - PowerPoint PPT Presentation

“Top-up” Operation at the Swiss Light Source

SPring-8 12/03/02

SLS at the Paul Scherrer Institute (PSI), Villigen, Switzerland

Michael B¨

• ge

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“Top-up” Operation at the Swiss Light Source

SPring-8 12/03/02

SLS Team at PSI

Michael B¨

• ge

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“Top-up” Operation at the Swiss Light Source

SPring-8 12/03/02

Contents

• Layout of the SLS
• Linac, Transferlines
• Booster
• Storage Ring (SR)
• Beamlines and Insertion Devices
• Important Subsystems for Top-up

– Pulsed Magnets – Digital Power Supplies – Timing System – Digital BPM System

• Top-up Operation
• Stability - Slow Orbit Feedback
• The Future

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“Top-up” Operation at the Swiss Light Source

SPring-8 12/03/02

SLS Layout

• Linac

– 100 MeV

• Booster

– 100 MeV to 2.7 GeV @ 3 Hz – ǫx = 9 nm rad

• Storage Ring (SR)

– 2.4 (2.7) GeV, 400 mA – ǫx = 5 nm rad

• Initial Four Beamlines:

MS – 4S, PX – 6S, SIS – 9L, SIM – 11M

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“Top-up” Operation at the Swiss Light Source

SPring-8 12/03/02

Linac - Design

100 MeV, 3 GHz S-Band “turn key” System:

• 90 kV grid gun: 1 ns pulse or 500 MHz train
• Sub-Harmonic Pre-Buncher (500 MHz)
• 4-cell Travelling Wave (TW) Buncher (β = 0.6)
• 16-cell TW Buncher (β = 0.95 → 4 MeV)
• 2 × 50 MeV TW Accelerating Structures (5.2 m, β = 1)

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“Top-up” Operation at the Swiss Light Source

SPring-8 12/03/02

Linac - Specifications, Diagnostics, Optics

SLS 100 MeV Pre− Injector Layout

Optics Gun, bunching section and first accelerating structure

Goal:

− Fast injection into the SLS storage ring (up to 200 mA/min).

Constraints:

− Narrow apertures of the innovative SLS booster synchrotron. − Radiation protection limitations.

Modes of operation:

− A single bunch mode (max. 1.5nC, 1ns). − A variable multi bunch mode (max. 1.5 nC). − In addition an optional low current mode is planned to

perform a top up injection, keeping the mean current in the storage ring nearly constant. Low energy region (up to 10 MeV):

− 31 solenoids.

Drift section at 50MeV:

− Quadrupole triplet to matches the beam through the

second accelerating structure. Two 35MW pulsed klystrons, TH2100 from Thomson, are used to power the travelling wave bunchers and the accelerating structures. The power distribution between bunchers and section 1 is performed by means of two variable power splitters. The RF power needs for a 100 MeV

• peration are listed here below.

RF distribution

500 MHz prebuncher 500 W 4 cell buncher 2.7 MW 16 cell buncher 3.7 MW Accelerating section 1 11.5 MW Accelerating section 2 18 MW Diagnostic description

Except the Integrating Current Transformers (standard ICT monitors from Bergoz) all the diagnostics have been developed at PSI and optimised to cover the large dynamic range of the SLS pre− injector. FCUP− 1 (Coaxial Faraday Cup)

− transient beam meas. behind the gun at 90 KeV. − bandwidth: >6 GHz − can be moved into a beam with pneumatic actuators

WCM− 1 and WCM− 2 (Wall Current Monitors)

− transient beam meas. behind the gun and in the transfer line at 100 MeV − cut− off: <100 kHz − bandwidth: ~4 GHz

ICT− 1 and ICT− 2 (Integrating Current Transformers)

− beam transmission efficiency trough Linac − resolution: <5%

BPM (strip line Beam Position Monitors)

− mismatch design for high sensitivity and max. aperture for low current Top− up mode

SMs − OPTICAL diagnostics

− six optical Screen Monitors (SM) have been used during the commissioning. All SM have been

intensively used for fine beam alignment and focus optimisation.

− SM− 5 and SM− E have been used for emittance and energy spread measurements. − two different monitors are installed in each SM station for high resolution measurements of the

transverse beam parameters:

a high sensitivity YAG:Ce detector for low current operation (charge < 1nC). an Al− foil producing Optical Transition Radiation (OTR).

− all SM monitors can be moved into the beam with 3 stage pneumatic actuators. Max single bunch width 1ns Bunch train length 0.2 − 0.9µs Max Charge 1.5nC (both modes) Energy >100 MeV Pulse −pulse energy stability <0.25% Relative energy spread <0.5% (rms.) Normalized emittance (1σ) <50 π πmm mrad Single bunch purity <0.01 Repetition rate 3.125 Hz, 10 Hz (max.) RF Frequency 2.997912 GHz Faults <1 fault/hour

Beam specifications

Linac main components

The electron source:

− A 90 kV triode gun with Pierce geometry. In the single

bunch mode the cathode is pulsed with respect to the grid. In the multi− bunch mode the grid is modulated at 500 MHz with respect to the cathode. The bunching section:

− SPB: 500 MHz sub− harmonic pre− buncher. − TWB1: 4 cells travelling wave buncher (b=0.6, 2p/3). − TWB2: 16 cells trav. wave buncher (b =0.95, 8p/9).

Two travelling wave accelerating structures:

− Structures based on SBTF design (b=1, 2p/3, 5.2 m

long).

The transfer lines:

− To the beam dump. − To the booster.

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“Top-up” Operation at the Swiss Light Source

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Linac - Measurements

single bunch multi− bunch

Single bunch width

1 ns

Multi bunch width

0.5 µs

Charge in a

bunch/ bunch train 2 nC 2.1 − 2.3 nC Energy 102 MeV 103 MeV

Pulse to pulse energy stability

<0.1% <0.1%

Energy spread (rms) 0.2% 0.3% Normalized emittance (1σ) 50 mm mrad 40 mm mrad Single bunch purity

<0.01

Repetition rate

3.125 Hz 3.125 Hz

RF reflected power interlock

trips

1 trip/4hours 2 trips/4hours

Acceptance test summary

During the acceptance tests, the long term stability of the system has been demonstrated within the specified beam parameters

Emittance @ 100 MeV Energy spread @ 100 MeV

Horizontal Beta: 9.871 m Alfa: − 1.758 rad Emittance: 14.7 mc mm mrad [9%]

Vertical Beta: 10.425 m Alfa: − 1.995 rad Emittance: 15.8 mc mm mrad [6%] Beam energy = 99.99 MeV/c

Rms energy spread = 0.089 % Dispersion = 0.831 m

energy 0.089% emittance x/y: spread:

~ 15/16 mm mrad

> 15 mm rad >0.089 %

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“Top-up” Operation at the Swiss Light Source

SPring-8 12/03/02 Linac - Linac-Booster Transferline

εx=0.7m Linac Bending ALIMA−BY 15/45 deg +−0.5 % Booster Horizontal Scraper Injection Kicker 0 m 19 m 34 m Linac−Booster Transferline

• +-0.5 % energy filtering -> 60 % of the charge remains for injection into the booster
• booster energy acceptance 7 % restricted to 2 % by the acceptance of the vacuum chamber at

100 MeV and 0.5 % by the maximum RF voltage of 0.5 MeV @ 2.4 GeV

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“Top-up” Operation at the Swiss Light Source

SPring-8 12/03/02

Booster - Design

– 3 FODO arcs with 48 BD (+SD) 6.4410 ◦and 45 BF (+SF) 1.1296 ◦ – 3 × 6 Quadrupoles for Tuning, 54 BPMs, 2 × 54 Correctors – ± 15 mm × ± 10 mm Vacuum Chamber – Energy: 100 MeV → 2.7 GeV, Repetition Rate: 3 Hz, Circumference: 270 m – Magnet Power: 205 kW, ǫx @ 2.4 GeV: 9 nm rad

Injection Storage Ring Linac Booster Injection

0 5 10 15 20 25m

O T R

Maximum Energy GeV 2.7 Circumference m 270 Lattice FODO with 3 straights of 8.68 m Harmonic number (15x30=) 450 RF frequency MHz 500 Peak R F voltage MV 0.5 Maximum current mA 12 Maximum rep. Rate Hz 3 Tunes 12.39 / 8.35 Chromaticities −1 / −1 Momentum compaction 0.005 pread, rms t 2.4 GeV Equilibrium v Emittance 9 Radiation l oss keV/ turn 233 Energy s 0.075 % Partition numbers (x,y, (1.7, 1, 1.3) Damping times (x,y, ms (11, 19, 14) alues a nm rad ε) ε)

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“Top-up” Operation at the Swiss Light Source

SPring-8 12/03/02 Booster - Ramp

0.4 0.8 1.2 1.6 2 2.4 2.8 40 80 120 160 200 240 280 320 energy [GeV] time [ms] booster ramp 2.4 GeV 100 MeV

• 0.04

0.04 0.08 0.12 0.16 0.2 50 100 150 200 250 300 350 400 450 500 current [mA] time [ms] MPCT

0.16mA 2.4 GeV 100 MeV 2.4 GeV 100 MeV 25 ms 25 ms −50 MeV 320ms

• Gas desorption by synchrotron light @ high energies (bad lifetime @ injection)
• Cosinusoidal “fast” Booster Ramp starts @ -50 MeV (injection @ 100 MeV after 25 ms)
• Tune/chromaticity correction through quadrupole/sextupole ramp tables (“wave forms”) (avoid

3Qx = 37, compensate eddy current induced sextupole components)

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