Present Light-source Activities and Future ERL Plans at KEK S. - - PowerPoint PPT Presentation

Present Light-source Activities and Future ERL Plans at KEK

• S. Sakanaka

Photon Factory, High Energy Accelerator Research Organization (KEK)

Site Map of KEK (High Energy Accelerator Research Organization)

KEKB PF storage ring PF-AR Neutrino Beamline

The Photon Factory at KEK

• Two synchrotron light sources

PF storage ring (2.5 GeV) PF-AR (6.5 GeV)

• More than 2,500 users

Number of users Operation time/year (PF-ring)

1000 2000 3000 4000 5000 6000

8 2 8 3 8 4 8 5 8 6 8 7 8 8 8 9 9 9 1 9 2 9 3 9 4 9 5 9 6 9 7 9 8 9 9 2

Total operation time Scheduled user's time Net user's time

Fiscal year Operation time (hrs.)

Scientific-field distribution

Photon Factory (PF) storage ring

• 1982 Commissioned.
• 1986 First low-emittance: 400 → 130 nm·rad
• 1997 Second low-emittance: 130 → 36 nm·rad

Inside photo. 0.014 Synchrotron tune 312 Harmonic number 500.1 MHz RF frequency (9.60, 4.28) Betatron tune (νx, νy) 36 nm·rad Natural beam emittance 187.03 m Circumference 2.5 GeV Nominal beam energy Principal parameters.

Layout of the PF storage ring

6C 7C 6B 6A 7B 4C 4B 4B 1 2 3C 3 4A B5 B6 B7 B8 B9 B10 B4 B3 B2 3C 1 3A 3B 2A 2C 1B 1C 3C 2 B1 B28 B27 28B 28A 27A 27B 27A 1 2 B26 B25 B24 B23 B22 B21 B11 B12 B20 B19 18A 18C 19A 19B 20B 20A 21 17B 18B 17C 17A 16B 16A 16A 1 2 15A B18 B17 B16 15C 14C1 14C2 14A 14B 13A 13C 12C 12A 11B 13B 13B 1 2 12B 11A 11D 10B 9C 9A 10A 8C 2 10C 11C 7A 8B 8A B13 B14 B15 T 15B T 25m

U#2 RF MPW#13 MPW#16 Revolver#19 EMPW#28 Injection VW#14 RF Six insertion devices 22 beamlines More than 60 experimental stations

Upgrade to the low-emittance lattice (1997)

• Each FODO-cell was reconstructed to two FODO-cells

Before reconstruction After reconstruction

Beam optics in the normal-cell section

Orbit stabilization using the global feedback system

• An integrated system for the beam-position measurement and the global feedback.
• This system can measure the COD in every 12 ms.
• Using fast-response correctors, we can correct the vertical orbit variations at

frequencies of up to 0.3 Hz.

Block diagram Photo of the VME system.

Damped accelerating cavities

• Harmful higher-order-modes can be damped by using

microwave absorbers (made of SiC) in the beam pipe.

• We tuned remaining trapped-modes so as to avoid any

coupled-bunch instabilities.

140 464 260 150 100

Cavity Fixed Tuner SiC Absorber

Cross section of one cavity unit. Damped cavities as installed.

Improvement in the beam lifetime by rf-phase modulation

Modulated rf voltage

2 4 6

• 2
• 1

1 2

Bunch

RF voltage (MV)

ωt

[ ]

) 2 cos( ) 2 cos( 1 2

2 2

t t

s s m s s

ω ω φ φ ω ε ω φ λ φ − = + + +

• 0 cotφ

φ ε

m

=

Modulate the rf phase at a frequency of 2ωs Parametric resonance

2 4 6 8 10 12

modulation Synchrotron

• scillation

Phase

2 4 6 8 10 12

ωst

Typical operation (24 hours)

02/04/11 09:00 02/04/11 21:00 02/04/12 09:00 20 40 60 80

Lifetime (hrs.) Date and Time

100 200 300 400 500

With phase modulation Current (mA)

April, 2002

PF-AR

Inside photo. 6.66 MeV Radiation loss / turn 640 Harmonic number 508.58 MHz RF frequency (10.15, 10.23) Betatron tune (νx, νy) 294 nm·rad Natural beam emittance 377.26 m Circumference 6.5 - 5 GeV Beam energy Principal parameters.

• 1986 Parasitic usage of SR from the TRISTAN booster ring.
• 1998 Switched to dedicated light source.
• 2001 Major upgrade

NE3 NW2 NE1 NE5

Notrh-East Experimental hall

NE9 NW12

North-West Experimental hall North Experimental hall

10 m

Upgrade of the PF-AR (2001)

New experimental hall New copper chambers New in-vacuum undulators Insertion devices in-vacuum: 3 conventional : 1 EPICS-based Control

In-vacuum undulator (NW-2)

Allows tapered configuration for XAFS experiments Spectrum range: 5 - 25 keV

NdFeB Type of magnet 3.6 m Undulator length 1.8 keV Typical 1st harmonic 0.8 T Peak magnetic field 90 Number of periods 40 mm Undulator period 10 mm Minimum gap Parameters

Courtesy: S. Yamamoto

Typical operation

10 20 30 40 50 60

PF-AR operation (Feb. 23-24, 2003)

10:00 5:00 19:00 14:00 0:00 14:00

Time Beam current (mA)

10 20 30 40 50

Lifetime (hrs.)

• Beam energy

6.5 GeV for usual experiments 5 GeV for medical application

• Full-time single bunch operation

Brilliance of the synchrotron radiation

1012 1013 1014 1015 1016 1017 1018 1019 101 102 103 104 105 Brilliance (photons/sec/mm2/mrad2/0.1%b.w.)

Photon energy (eV)

PF E=2.5GeV, I=400mA ε=36nmrad 1% coupling PF-AR E=6.5GeV, I=50mA ε=168nmrad 1% coupling

Revolver #19

A B C D

U#02 AR-NE#03 MPW #13-U MPW #16-U MPW #16-W MPW #13-W AR-EMPW #NE01 EMPW #28 PF-Bend AR-Bend VW#14

Future plan: Energy Recovery Linac based light source

Suitable balance for two requirements is very important for the Photon Factory.

• Provide highly-advanced tools for investigating, analyzing,

and processing materials.

• Provide wide-purpose, high performance tools with

sufficient capacity for investigating new materials. ERL-based light source is being recognized as the most promising light source.

Requirements from the scientists

• Spectrum range : from soft x-ray to hard x-ray
• Average brilliance (at 0.1 nm) : > 1022 ph/s/0.1%/mm2/mrad2
• Average flux : > 1016 ph/s/0.1%
• Pulse length : < 1 ps is available
• Beam stability : less than 1/10 of beam sizes

Tentative ERL plan at KEK

• Beam energy : 2.5 GeV (phase I) - 5 GeV (phase II)
• Provide the 1st harmonic undulator radiation of 1 Å with an

undulator period of 15 mm (present minimum).

• Insertion devices: 5 m × 12, 30 m × 4, 200 m × 1

407 m 279 m U200

U30 U30 U5 U5 U5 U5 U5 U5 U5 U5 U5 U5 U5 U5 U30 U30

615 m

E=2.5 - 5.0 GeV C=1253 m

Principal parameters (goal)

10 pm·rad Beam emittance at 5 GeV 10 - 20 MV/m Acceleration gradient 1.3 GHz RF frequency 1 - 0.1 ps Bunch length (r.m.s.) 5×10-5 Energy spread (r.m.s.) 0.1 mm·mrad Normalized beam emittance 1253 m Circumference 100 mA Average beam current 10 MeV Injection energy 2.5 - 5.0 GeV Beam energy

• Aims at realizing diffraction-limited light source at the photon

energy of about 10 keV

• Requirements for electron sources and for emittance preservation

will be very stringent.

Standard 5m undulator

Spectrum range of undulator radiation from a standard 5 m undulator.

By S. Yamamoto

Anticipated spectrum for long undulator

Calculated brilliance for 30, 60, 100, 120 and 200-m undulators. Undulator period: 2.0 cm, beam current: 100 mA. Optimized betatron functions for each undulator lengths were used. Requirement for the energy spread

kN E

E

4 1 ≤ σ

By S. Yamamoto

Superconducting accelerator

Performance of L-band single-cell accelerating cavities which were treated using Electroplishing (EP) technique at KEK.

• High-gradient of up to 40 MV/m have been achieved with L-band

superconducting cavities (DESY/Cornell/JLab/KEK).

108 109 1010 1011 10 20 30 40 50

K-14 : half cell annealed at 1400

• C, EP, HPR, Bake

K-8 : BP, 760

• C anneald, EP, HPR, Bake

K-9 : BP, 760

• C annealed, EP, HPR, Bake

JL-1 : fabricated at CEBAF, CP, EP, HPR, Bake K-11 : CP, 760

• C annealed, EP, HPR, Bake

K-22 : CP, EP, HPR, Bake

Qo Eacc [MV/m] 1.5 ~ 1.8 K

For the ERL: 10 - 20 MV/m

Courtesy: K. Saito

High-gradient with 9-cell cavities

Performance of DESY 9-cell cavities which were treated using Electroplishing (EP) technique at KEK.

• High-gradient performance has also been demonstrated with 9-

cell cavities which were treated by the EP technology.

10

8

10

9

10

10

10

11

5 10 15 20 25 30 35 40 DESY CP+HPR (lower Q) DESY CP+HPR (higher Q) AC72 : EP(KEK)+HPR(DESY)+Bake(DESY) AC73 : EP(KEK)+HPR(DESY)+Bake(DESY) AC78 : EP(KEK)+HPR(DESY)+Bake(DESY) Qo Eacc [MV/m] TESLA500 Specification TESLA800 Specification

Courtesy: K. Saito

Superconducting accelerator for the ERL

• TESLA-type 9-cell cavities, 1.3 GHz, operated at 2K
• Accelerating gradient : 20 MV/m (phase I: 10 MV/m)
• Key technology for high gradient:

Electropolishing (EP), High-pressure water rinsing, etc.

• Cost reduction: Nb-Cu clad seamless cavity

Simplification of the treatments

• Higher-order-mode damping and tuning
• Engineering design of cryomodule, reduction in length

Parameters of ERL superconducting cavities based on TESLA-type design

10 - 20 MV/m Operation gradient 29.6 W/cavity at 2K (at 20 MV/m) 7.4 W/cavity at 2K Dynamical heat loss (at 10 MV/m) 130 Hz (FWHM) Cavity bandwidth at Qext = 1 × 107 1 × 107 Qext of input coupler 315 kHz/mm ∆f/∆L ±315 kHz Tuning range 42.6 Gauss/(MV/m) Hp/Eacc 2.0 Ep/Eacc 1036 Ω R/Q 70 mm Iris diameter 1.87 % Cell-to-cell coupling kcc 1.036 m Active length L 1.5 × 1010 Unloaded quality factor Q0 1300 MHz Accelerating frequency

Heat loads for cryogenic plant

1.5 1.3 Safety factor for Q-value 1.5 × 1010 1.5 × 1010 Q0 8.9 kW (4.3 K equiv..) 500 W (equiv. 4.5 K) 337 W (at 4.3 K equiv.) 10 W (at 4.3 K equiv.) 20 W 18 W (at 4.3 K equiv.) 74 W (at 2K) 222 W (4.3 K equiv.) 10 MV/m Phase I (2.5 GeV) 20 MV/m Gradient 35 kW (4.3 K equiv.) Total heat load for 25 modules 500 W (equiv. 4.5 K) Transfer loss 1 km 1380 W (at 4.3 K equiv) Total heat load/module 10 W (4.3 K equiv.) Heat leaks at 80 K shield/module 20 W Heat leaks at 4.5 K shield/module 18 W (at 4 K.3 equiv.) Heat leaks at 2 K shield/module 296 W (at 2K) 888 W (4.3 K equiv.) Dynamical loss/(10 cavities) Phase II (5 GeV)

• Phase I : 10-kW (at 4.3 K) class cryogenic plant
• Phase II: add three more 10-kW class plants

Design issues of the arc

• Minimize emittance growth and energy spread due to

1) incoherent SR 2) coherent SR

• Variable R56 for bunch compression / no-compression

Compensation for higher-order terms (T566 etc.)

• House many undulators (requirement: about 20)

Optimum optics for undulators.

• Precise circumference control
• Tunable betatron phase advance per arc (for multibunch BBU)
• Limitation due to site

Preliminary design of the arc (unit cell)

TBA lattice 7-m straight for I.D. ρ = 17 m Beam optics for unit cell. Designed by Y. Kobayashi Tuning range for R56 (-0.1 to 3.4 cm)

Preliminary design of the arc

by Y. Kobayashi Lattice configuration of π-arc Beam optics for the complete arc

Beam dynamics issues

• Multibunch BBU effect and other issues have been investigated

by Y. Shobuda.

• Under simulations, it is possible to obtain the threshold current
• f more than 100 mA for the multibunch instability by adjusting

betatron phase advance per circulation, and by other means. Simulation model Courtesy:

• Y. Shobuda

Electron sources

• Ultra-low emittance (0.1 π•mm•mrad) and high average current (100 mA)

require very ambitious challenges for electron sources.

• Some experience on RF photocathode gun at KEK.

(BNL/Waseda-U/KEK/Tokyo-U/Spring-8)

• Photocathode RF gun seems to be not very promising for the ERL

1) Very difficult to reduce the emittance below 1 π•mm•mrad 2) Under CW operation, one must lower the field gradient considerably

• DC photocathode gun seems very promising (GaAs NEA)

1) High quantum efficiency (but short lifetime of cathode) 2) Ultra-low emittance ( < 1 π•mm•mrad) is possible, in principle 3) Long-time experiences as the polarized sources (but low-currents)

• KEK is pushing R&D for DC photocathode guns under collaboration with

Nagoya Univ. (Prof. Nakanishi et al.)

Summary and present status of KEK-ERL plan

• During the past year, a preliminary planning was carried out.
• Based on the tentative plan, an interim report "Study Report on

the Future Light Source at the Photon Factory" is being published as the KEK report (in Japanese).

• Trying to make a consensus among the users.
• Investigations on many issues are under way.
• R&D for the superconducting technologies, precise short-

period undulators, etc., are progressing as natural extensions.

• R&D for ultra-low emittance electron source has started.