Transcript Document 7834629

PHIN
R. Losito
CERN – AB/ATB
05/09/2005
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP1: Management
 Website created
 Maintainance and upgrade
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP2: Charge Production
 3 GHz RF Gun
 High efficiency photocathode comparison
• Intermediate report done
• Final report: reported to end of 2006 (no news from Twente..).
• Photocathode preparation equipment construction
– Under way, delays due to problems in refurbishing certain
components, production of photocathodes should restart in
November at CERN.
• Photocathode 3 GHz high field R&D
– Dark current measurements, thin fim adherence under high
field etc..
– Will start after arrival of the RF Gun (December/January?)
» Milestone will probably slip by some months
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP2: Charge Production
 Photocathodes for SC Cavity
 Photocathode preparation equipment ready (31/03/05)
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
FZR SRF Photogun – Cathode Preparation
The photocathode preparation system was
completely assembled and its function
was tested. It contains two pairs of
evaporators for Te and Cs, the holder
and heater for the cathode with
temperature measurement, a motor
driven shutter, a measurement aperture
for photo current, and two deposition
rate monitors allowing co-evaporation,
and is equipped with a 262 nm, 10 mW
laser system. The computer control system
(electronics and software) is ready.
At present, the system is disassembled
and the parts are being cleaned. After
that, the system will be assembled again
in the clean room.
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP2: Charge Production
 Photocathodes for SC Cavity
 Photocathode preparation equipment ready (31/03/05)
• The new preparation equipment was installed and tested. At
present it is being cleaned for installation in the clean room.
 Photocathodes tests
• Will start when material ready.
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP2: Charge Production
 Laser Driven Plasma source
 No fresh news from LOA …..
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP3, T1: LASER
 Laser for the CTF3 Photoinjector:
 All the milestones have shifted by ~6 months due to the late
arrival of funding and long procurement delays due to
specificity of the material.
 An important deliverable reached is the laser oscillator: Built by
HighQLaser (Austria), it is the first of his kind with
• rep rate of 1.5 Ghz
• rms pulse lenght < 10ps
• Jitter < 1 ps
• Amplitude stability < 0.2 %
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP3, T1: Oscillator and preamplifier
The results of the acceptance tests:
HighQ acceptance tests Notes
Laser repetition 1.4993 GHz
rate
RAL acceptance tests
Adjustable using a
translation stage on a
cavity mirror

Average power
10.3 W
 10.5 W
Pulse width
5.3 ps

Beam quality
M2 = 1.1
Measured with
Coherent Mode Master

Long term
stability
0.56% rms
Over 13.5 hours

Timing jitter
123 fs (electronic)
Measured with
electronic mixer and
also with optical
reference oscillator,
using cross-correlation
 71 fs (electronic)
126 fs (optical)
 99 fs (optical)
The oscillator and preamplifier are now working to specification at RAL
The additional preamplifier has delivered the required power
The improved timing jitter seems to be due to low environmental noise at RAL
Anomalous photodiode measurements at CERN have been resolved
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP3,T1: Amplifier procurement
Amplifier 1
Amplifier 2
Laser diodes


Laser diode drivers


Focusing lenses


Laser rod


Mechanical components


Water chiller




Beam transport optics
Optomechanics

Diagnostics

Breadboard

Specified 
Ordered

Delivered 
R. Losito CERN-AB-ATB
Amplifier 1 assembly and testing will begin in September
Amplifier 2 assembly and testing will begin in November
Care Steering Committee, Paris, 05/09/2005
WP3, T1: Updated layout of the system
350 cm
Coding
Thermal lensing
compensation
Table at RAL
Beam size provided
for 1st amplifier
Beam size provided
for FHG
HighQ amplifier
Laser beam to cathode
Diagn.
Delay line
Beam size provided
for SHG
Faraday isolator
Diagn.
150 cm
Pockels cell(s) for
generating 1.5 us train
1st amplifier
Beam size provided
for 2nd amplifier
Diagnostics
FOM system
Feedback
stabilisation
HighQ oscillator
2nd amplifier
Breadboard
Amplifier beam heights ~ 12 cm
: alignment check camera
Table at CERN
: calibrated PD for power monitoring
• Recent modifications include final layout of HighQ system, extra diagnostics and “inversion”
of the overall scheme to improve stability of beam delivery to the accelerator vault
• A timing and control system, compatible with the CERN architecture, has been specified
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP3, T1: Time & Amplitude Structuring
PULSE SLICING
• Needs two large-aperture Pockels cells (single-pulse and 1.54ms train) to handle high
average power after Amplifier 2
• Current design includes programmable corrector to reduce systematic pulse
amplitude variations to <0.1% RMS
• System is commercially available
AMPLITUDE STABILISATION
• If the intrinsic amplitude noise is low then a low-retardance Pockels cell will be
adequate, requiring low drive voltage compatible with fast electronic amplifiers
• Performance will be dominated by the sensor and the feedback control electronics
• Sensor and cell are commercially available but FC electronics need specialist design
PULSE CODING
• Requirement for a 7 MHz, multi-kV, drive waveform with <300ps switching time and
better than 1% amplitude control makes a system based on a Pockels cell unviable
• The alternative is a fibre-optic (FO) modulator system placed after the oscillator
where the average power is low
• The >10dB losses of an FO system will require more gain from the preamplifier
• The FO system is commercially available and the preamplifier’s manufacturer can
increase its gain, but this will involve some delay, best left to the end of the program
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP3, T1: Fast pockels cell drivers
New Fast Ionization Devices (FID) and Drift Step
Recovery Diodes (DSRD)
Customization of standard product. E.g:
FPG-05-10S
Output voltage at 50 Ohm
2-5 kV
Pulse width at 90% of Umax
0.3-0.5 ns
Rise time
<100 ps
Fall time
<500 ps
Maximum repetition rate
10 kHz
Timing stability (jitter)
< 20 ps
Maximum sync/output delay time
100-150 ns
Input trigger
5V
Power supply, DC
300 V
Dimensions
100x50x40 mm
R. Losito CERN-AB-ATB
New devices developed by the Ioffe
Physical-Technical Institute of Russia
Academy of Science in St. Petersburg.
They are based on a new physical
phenomenon: the elctrone-hole plasma
supergeneration in solid state. This
permits to have high operating voltage
up to 5kV and the turn-on time less
than 1 ns.
The DSRD are diodes characterized
by fast voltage restoration that assures
low commutation jitter, unlimited life
time, repetition rate that can be as high
as megahertz and opening times can
be less than 1 ns with 100 A current.
Care Steering Committee, Paris, 05/09/2005
WP3, T1: (LASER) Timescales and deliverables
CARE SC Apr 2005 Current (Sept 2005) Deliverable
Notes
03/2004
 03/2004
Report on laser oscillator
design
06/2005
 06/2006
Laser oscillator test
results
06/2005
10/2005
Report on laser amplifier
design
Laser oscillator and
preamplifier working to
specification at RAL.
Amplifier design complete
& procurement under way.
Report delayed to speed
up procurement.
12/2005
02/2006
Report on UV conversion Moved to follow amplifier
crystal comparison
tests.
11/2005
01/2006
Amplifier test results
Delays in procurement.
06/2006
06/2006
Laser system test results
and delivery to CERN
Staff deployment is being
revised to hold delivery
date (coding system may
cause delay).
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP3, T2: Shaping of the UV laser pulse
UV time profile measured using a
multishot cross-correlator with 200 fs resolution.
It is possible obtain rise-time < 1 ps and ripples < 30%
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP3, T3 : Low rep rate synchronization tests at LNF
High energy UV
@ 10 Hz
19.0
18.5
18.0
Phase [deg]
17.5
17.0
16.5
16.0
15.5
2856 MHz cavity
15.0
-20
0
20
40
60
80
100
120
140
160
Time [s]
500
laserYpulses
Axis Title
400
On time scale of few minutes (enough to
adjust the RF) the phase jitter is
300
200
within σRMS 0.63 deg [0.61 ps].
Further characterizations are foreseen.
100
0
14
15
R. Losito CERN-AB-ATB
16
17
X Axis
Title
phase
[deg]
18
19
Care Steering Committee, Paris, 05/09/2005
WP4, T1: FZR SRF Photogun
Superconducting Nb cavities:
The two cavities were delivered
by ACCEL in March 2005.
One is made of high-quality
Nb RRR 300 for use in the gun,
one of Nb RRR 40 for tests
(instead of a Cu model, which
additionally allows to check
e-beam welding, warm tuning,
and chemical treatment etc.)
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP4, T1: FZR SRF Photogun – RF Measurement and Tuning
1: Sensors-vertical position, 2: Sensors horizontal Pos.,
3: DC-Motor (bead pull drive), 4: Stepper motor (vertical
pos.), 5: Motor control box, 6: Sensor hardware,
PC-controlled bead pull measuring device
(principle) built at FZR in 2005.
R. Losito CERN-AB-ATB
3D-CAD-Model of the tuning machine
used for warm tuning (to push and
pull each cell to the right frequencies).
The special cavity shape required to
build such a machine at FZR.
Care Steering Committee, Paris, 05/09/2005
WP4, T1: FZR SRF Photogun – Warm Tuning
Field profiles from bead pull measurements.
Photograph of the cavity tuning machine
with integrated bead pull measuring device.
R. Losito CERN-AB-ATB
Before chemical treatment, warm tuning
of the cavities has been carried out in order
to obtain the right frequency and the
designed field profile (equal amplitudes in
the three TESLA cells and 64% in the
half-cell).
Care Steering Committee, Paris, 05/09/2005
WP4, T1: FZR SRF Photogun – Cathode Cooling System
Cathode with
heater
Cooling body
Liquid nitrogen
reservoir
The test of the cathode cooling system
has been succeeded. In the SRF gun,
the normal conducting cathode is inside
the SC cavity. With the test was proofed
whether the cathode heat load (from rf
field) will be transported into the liquid
N2 cooler. It was found that the cooling
system works well and only a small
amount of the heat (some mW) will be
transferred to the SC cavity.
The cathode cooling system mounted on the
test bench flange. The rf heat load is simulated
by an electrical heater (10 – 50 W).
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP4, T1: FZR SRF Photogun – Project Status
CAVITY:
Two Nb cavities (NbRRR300 + RRR40) have been delivered.
Rf-tests and warm tuning has been performed at FZR. Chemical treatment
will now start at DESY.
CRYOMODULE:
Most of the main components (vacuum vessel, 80 K cryo-shield,
magnetic shield, support frame, rf coupler, tuner, cathode cooler, cathode
transfer system) have been delivered. Cathode cooler test has succeeded.
The tuner test is under way. He transfer line is ordered.
PHOTO CATHODES:
The new preparation equipment was installed and tested. At present,
it is being cleaned for installation in the clean room.
LASER:
The upgrade of the driver laser system is under way (MBI).
DIAGNOSTICS:
a diagnostics beam line is designed. The realization has started (BESSY).
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP4, T1: 3GHz RF GUN
 WP4 RF GUNS STATUS
 1st RF Gun construction
 After many tries of the manufacturer to do a elliptical shape, a compromise was
done: irises are done in 12 facets and it meets the specifications.
ordered in the end of April, 4 months of delay, delivery in beginning of
September
 Measurements and mechanical adjustments are planned for one month,
delivery of the gun by the end of December if everything goes well
 RF gun at LAL
 Laser was ordered to Opton Laser in July, delivery in 4 months
 NEPAL room

Shielding
• Other Radio-protection study is under way to reduce the cost
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
WP4, T1: Spectrometer for e-beam
 No News from LOA
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005
Conclusions
 Work generally on track for CTF3 photoinjector,
Photoinjector at LAL, SC RF Gun and studies of pulse
shaping in Frascati.
 Due to holidays and to injury of Andrea, difficult to get
information about Twente, INFN – Mi, Loa.
 Should be addressed at the next collaboration meeting.
R. Losito CERN-AB-ATB
Care Steering Committee, Paris, 05/09/2005