the atf operations performance and upgrade

Operated by Brookhaven Science Associates for the U.S. Department of Energy

The ATF OperationsPerformance and Upgrade

X.J. WangAccelerator Test Facility

NSLS, BNLUpton, NY 11973

Presented at the CAP Steering Committee and ATF Users MeetingJanuary 31 – February 1, 2002


Acknowledgement

The success of the ATF made it possible due to:• Support from Advanced Technology Program of

DOE High Energy Physics.• Support from BNL director’s office and NSLS.• ATF users and collaborators.• Dedicated ATF staff.


ATF operations

Since the last ATF user meeting, we provided about 2000 hours beam time for:

• 9 experiments – Smith-Purcell, Compton, Stella II, Dielectric Wake field, HGHG, VISA, MINOS, Optical detector, linear collider BPM.

• Two PhD thesis -• Three experiments finished – HGHG, VISA and MINOS.

ATF experiments continue to produce good physics:1. Stellar experiment.2. Only facility has both laser seeded and SASE FEL saturated, shortest

gain length and the highest gain.3. Record X-ray yield from Compton Experiment.4. First observation of coupling between the longitudinal distribution and

transverse detection in cavity BPM.5. And many more …


Accelerator Test Facility Layout


0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0 0.5 1 1.5 2

Bun

chin

g -

sqrt(

CTR

(V))

SASE (V)

Fundamental Microbunching vs. SASE

Microbunching peaks

Microbunching/SASE linearly related

0.51

0.64

0.77

0.9

1

1.2

1.3

0 0.5 1 1.5 2 2.5 3 3.5

Mic

robu

nchi

ng

-sqr

t(CTR

(V))

SASE (V)

2nd Harmonic Microbunching vs. SASE

VISA

Micro-bunching measurements

E-beam and SASE

SASE

CTR


ATF operations

ATF had added new capabilities and carried out exploratory R&D:

1. TW CO2 Amplifier starts to serve users.2. Permanent magnets for small beam production.3. New electron beam spectrometer.4. New linac water system.5. New magnet power supply.6. New Leak detector and IR camera.7. High-brightness electron beam R&D.8. Vacuum acceleration and surface roughness studies.


Performance

• Photocathode RF gun – the brightest photoelectron sources in the world.1. Bunch charge from 1 pC to nC, bunch length

from 1 ps to 10 ps (FWHM).2. Emittance as small as 0.8 mm-mrad for a 100 A

peak current, routinely delivery < 2mm-mrad.• ATF laser systems – Yag laser provides the

most stable beam for photocathode RF gun, CO2 starts showing its potential.


Performance –High Brightness Electron Beam R&D

Mg cathode and vacuum laser cleaning works great.

140 160 180 200 220 240 260 2800

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

RF Gun Phase (Deg.)

Phot

oele

cton

bea

m c

harg

e (n

C)

Laser energy 2.2 uJ

Emittance vs. launch phase

00.05

0.10.15

0.20.25

0.30.35

0.40.45

0 20 40 60launch phase(degree)

90%100%

Sigma-Z at gun exit vs. launch phase for different Charge

0123456

0 50 100launch phase

Sigm

a-Z(

ps)

0.2nc0.5nc1nc


Performance - YAG Laser System� � Photocathode and CO2 slicing fully available on-demand.

� Electron beam-synchronized optical pulses available for users:

5 mJ, 14 ps @ 1064 nm in laser lab (exclusive of slicing)50 mJ, 10 ps @ 532 nm in laser lab or FEL room (not yet implemented)

50 mJ, 8 ps @ 266 nm in gun hutch and laser lab• Delivered light on 245 days since last user’s meeting (June 1, 2000)

Average ~10 hours/day.

Turn-on time usually 15 minutes, including daily performance characterization. Gun operations typically underway by 9:30 AM.


Performance - YAG Laser System

0 50 100 150 200 250

350

300

250

200

150

100

50 100 150 200 250 300 350 400 450 500 550 6000

100

200

300

Laser Energy Histogram

-8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4

Variation from mean [%]

Freq

uenc

y [a

rb. u

nits

]

�=1.1%

7500 shots

Laser Energy Shot-to-Shot Jitter

6.7

6.9

7.1

7.3

7.5

7.7

0 2000 4000 6000Shot Number

Ener

gy [�

J]

ATF Laser Oscillator-to-Clock Relative Phase [ps]

-2.2

-2.1

-2

-1.9

-1.8

-1.7

-1.6

-1.5

-1.4

1/12/200116:00

1/12/200122:00

1/13/20014:00

1/13/200110:00

1/13/200116:00

1/13/200122:00

1/14/20014:00

1/14/200110:00

1/14/200116:00


Performance – CO2 Laser System


Performance - Spectrometer

�New spectrometer has classical ��2 or 90 degrees design.

�It provides tight focus and large dispersion.

�The energy resolution is going to be of the order of 10-4 and will be limited by energy spread in the beam.


Upgrade

Short and medium term:1. Shorten the ATF CO2 laser pulse length and increase its power

toward TW level.2. Finish ATF computer system upgrade.3. Install ATF new H-line and bunch compressor.4. Install new ATF low level RF system.5. New software tools for users.6. Deformable mirror for photocathode RF gun laser optics.Long term:

1. ATF linac system upgrade to 120 MeV.2. New ATF beam lines and experimental hall.3. Solid state modulator and 1 kW amplifier.4. New solid state laser system for photocathode RF gun.5. TW femto-seconds solid state laser.6. Beam based feed back and control system system – test bed for

remote accelerator operation.


Upgrade -ATF CO2 Laser System

A Panel was assembled on Sept. 10 and 11, 2001 to review and advise the ATF on the CO Laser system upgrade plan:

1. Considering other CO2 pulse shortening technique.2. New high pressure pre-amplifier.3. Improve the oscillator performance.4. Optimize the Amplifier performance.

TW CO2 Laser system is expected to be operation by late 2002


Upgrade -ATF Computer Control System

Major effort over the last year to upgrade the control system

New hardware purchased and installed:• Host computer• Mass storage expansion• Ethernet-based CAMAC crate controllers• Private Ethernet for ATF control & data acquisition• For future use: Private fiber optic cables to all areas of ATF• Hardware firewall to protect ATF subsystems

New software purchased and installed:• Linux OS• Driver libraries for Ethernet crate controllers• Vsystem for Linux• Portland Group compilers


Upgrade - ATF Computer Control System

Porting ATF software:• All graphic operator displays have been converted for Linux• All supporting databases have been converted for Linux• All intermediate-level CAMAC libraries ported to Linux• In progress: porting of ATF server applicationsUsers can expect:• Same services as now (operator displays, network access, etc.)• Improved throughput• Better system reliability (easier to troubleshoot & maintain)• New software tools• Eventual support for new hardware families

New control system will be in operation in the fall of 2002.


Upgrade – ATF H-line

Install new quadrupole magnets support and alignment systems, better beam diagnostics and new chicane magnet bunch compressor:

1. Beam based alignment system to better and easier preserve the high brightness electron beam.

2. Give ATF more capabilities in short bunch production and diagnostics.

ATF H-line Upgrade will be implemented in the summer 2002.


Upgrade – ATF H-line


Summary

ATF and its experimental program have delivered first class results in beam physics. We have a plan to continue its success. To realize those future successes, your support and advise are the key.

Thank you.

the atf operations performance and upgrade

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