Aucun titre de diapositive

1
Accelerator Physics and Design Working
Group Summary 2/2
O. Napoly
2
CEBAF Energy Recovery ExperimentMichael
Tiefenback

• GeV scale Energy Recovery demonstration.
  Testing the potential of ERLs
• Demonstration of high final-to-injection energy
  ratios - 201 and 501
• Optimized beam transport in large scale
  recirculating linacs (320 SC cavities) - RF
  steering and skew field compensation for
  accelerated/decelerated beams

3
CEBAF Energy Recovery ExperimentMichael
Tiefenback
rf power measurement - selected cavity at the end
of South Linac
Standard arc BPMs go dead with ER beam - BPM
signal at RF fundamental - Decelerated beam is
?/2 delayed from primary beam signals
destructively interfere in BPM antennae
4
CEBAF Energy Recovery ExperimentMichael
Tiefenback
5
CW Energy Recovery Linac for Next Generation of
XFELs General Thoughts based on TESLA
XFEL-TDR TJNAF A. Bogacz
INFN M. Ferrario, L. Serafini DESY
D. Proch, J. Sekutowicz, S.
Simrock BNL I. Ben-Zvi LANL P.
Colestock UCLA J. B. Rosenzweig
TESLA_TTF Meeting Frascati, May 26-28,
2003
6
Possible layout can be very similar to the
present pulsed linac
1.8 km
3 km
3xSASE 2xUndulators
Dump (0.5 MW)
RF-Gun ?
BC I 0.14 GeV
BC II 0.50 GeV
R150 m
En 1020 GeV
BC III 2.50 GeV
energy recovery 95
7
Any combination of the bunch charge and the
spacing of bunches giving nominal current is OK
Example 1 mA 1 nC _at_
spacing 1 µs
8
Conclusion
Needed RD cw RF gun suppression of
microphonics more experience with the energy
recovery
Total cost without experiments should be lt 400
MEuros
Total AC power for Cryoplant RF lt 10 MW
But we will have 6 x more bunches /s
very flexible time structure of the beam.
9
Towards a Superconducting High Brightness RF
Photoinjector M. Ferrario, J. B. Rosenzweig, J.
Sekutowicz, L. Serafini INFN, UCLA, DESY
TESLA Meeting - Frascati - 27 May 2003
10
Main Questions/Concerns

• RF Focusing vs Magnetic focusing ?
• High Peak Field on Cathode ?
• Cathode Materials and QE ?
• Q degradation due to Magnetic Field ?

11
Measurements at room T on a dedicated DC system
Extrapolation to Higher Field
SCRF GUN
Measured
Limited by the available voltage
12
Splitting Acceleration and Focusing

• The Solenoid can be placed downstream the cavity
  
• Switching on the solenoid when the cavity is
  cold prevent any trapped magnetic field

13
scaling laws for Q and Epeak available
14
Progress on Helical Undulator for Polarised
Positron Production

• Duncan Scott
• ASTeC
• Daresbury Laboratory

15
SC Magnet Undulator Prototype

• Prototype Magnet Design for 14mm period
• Beam Stay Clear 4mm
• Helix Diameter 6mm

16
Permanent Magnet Undulator Design

• 14mm Period, 4mm Bore Halbach undulator
• (Klaus Halbach NIM Vol. 187, No1)

• PPM blocks create Dipole Field

• Rotate many rings to create Helical Field

17
Progress on Helical Undulator for Polarised
Positron Production

• Vacuum Problems
• TESLA requirements of 10-8 mbar vacuum CO
  equivalent
• For the SC magnet
• this can be achieved, as long as the number of
  photons above 3eV hitting the vessel wall is not
  greater than 1017 s-1 m-1
• For the Permanent magnet
• theoretical maximum for a 5 m long 4mm bore
  vacuum pipe is 10-7mBar
• A NEG coated vessel is needed, thought to be
  feasible although no-one has ever NEG coated a
  4mm diameter tube
• Hope to build two 20 period prototypes (one of
  each design) to measure the magnetic field this
  year

18
TESLA Damping Ring Injection/Extraction
Schemes with RF Deflectors

• D. Alesini, F. Marcellini

19
CTF3-LIKE INJECTION/EXTRACTION SCHEME (simple
scheme)
LINAC TRAIN
Extraction
Injection

• If the filling time (?F) of the deflectors is
  less than ?TDR it is possible to inject or
  extract the bunches without any gap in the DR
  filling pattern.
• ?? should be ? ?? depending on the ring optics
  and septum position. Considering a single RF
  frequency ?
• ? ??/?MAX1-cos(2?/F)

Rec. factor
20
3 Frequencies
3 distant freq. case
?
3 close freq. case

• maximization of ????MAX
• in the range 4301/ ?TL? 4501/ ?TL 1.276
  ? 1.335 GHz
• ? no bunch length

DEFLECTOR PARAMETERS (?/2) 6 Deflectors (3 inj.
3 extr.) Defl 1 ? fRF1 4331/ ?TL 1284.87
MHz Defl 2 ? fRF2 4381/ ?TL 1299.70
MHz Defl 3 ? fRF3 4431/ ?TL 1314.54
MHz Total beam deflection 0.87
mrad Deflection defl.1 0.29 mrad Deflection
defl.2 0.29 mrad Deflection defl.3 0.29
mrad
P 9 MW L 0.64 m ?F 48 nsec n.
Cells/defl 11
P 5.00 MW L 0.86 m ?F 64 nsec n.
Cells/defl 15
21
FINITE BUNCH LENGTH

• ?z6 mm, the same 2 freq. optimized in the
  previous
• case give

Extracted bunch
????1 9

• New optimization procedure
• to increase ????1
• (if possible) to reduce the RF
• slope over the bunch length

How to avoid the effect of the RF curvature on
the extr. bunches
22
3 Frequencies
? maximization of ????1 in the range
4301/ ?TL? 4501/ ?TL 1.276 ? 1.335 GHz ?
bunch length ?z6 mm
3 close freq. case
3 distant freq. case
?
DEFLECTOR PARAMETERS (?/2) 6 Deflectors (3 inj.
3 extr.) Defl 1 ? fRF1 4441/ ?TL 1317.51
MHz Defl 2 ? fRF2 4371/ ?TL 1296.74
MHz Defl 3 ? fRF3 4351/ ?TL 1290.80
MHz Total beam deflection 1.05
mrad Deflection defl.1 0.35 mrad Deflection
defl.2 0.35 mrad Deflection defl.3 0.35
mrad
????1 57
P 9 MW L 0.78 m ?F 58 nsec n.
Cells/defl 13
P 5.00 MW L 1.04 m ?F 77 nsec n.
Cells/defl 18
23
F100 ? LDR?2.85 Km
? maximization of ????1 in the range
4301/ ?TL? 4501/ ?TL 1.276 ? 1.335 GHz ?
bunch length ?z2 mm
3 distant freq.
????1 28
DEFLECTOR PARAMETERS (?/2) 6 Deflectors (3 inj.
3 extr.) Defl 1 ? fRF1 4471/ ?TL 1326.41
MHz Defl 2 ? fRF2 4401/ ?TL 1305.64
MHz Defl 3 ? fRF3 4361/ ?TL 1293.77
MHz Total beam deflection 2.16
mrad Deflection defl.1 0.72 mrad Deflection
defl.2 0.72 mrad Deflection defl.3 0.72
mrad
P 9 MW L 1.6 m ?F 119 nsec n.
Cells/defl 28
P 5.00 MW L 2.15 m ?F 160 nsec n.
Cells/defl 37
24
OUR EXPERIENCE WITH RF DEFLECTOR FOR CTF3
2. MECHANICAL DRAWING
1. STUDY AND NUMERICAL SIMULATIONS
4. MEASUREMENTS
3. CONSTRUCTION
25
p/2 MODE Deflection 0.5 mrad fRF 1.3
GHz Disk thickness 11.53 mm Cell length 57.65
mm
26
Beam Position Measurements in TTF Cavities using
Dipole Higher Order Modes

• G. Devanz, O. Napoly, CEA, Gif-sur-Yvette
• Gössel, S. Schreiber, M. Wendt, DESY, Hamburg

Module II
Module III
ON
OFF
Beam
HOM 2
q 3.5 nC fb 2.25 MHz Tp 780 ms
HOM 1
Agilent E8563E spectrum analyser
Spectrum analyser

• used as aparametric bandpass filter
• central frequency
• resolution bandwidth
• signals in time domain

GPIB
Att 10 dB
zero span
27
Dipole mode measurements
2 positions computed using 2 modes with the same
beam
High gradient in cavities ( 20 MV/m) ? orbit is
expected to cross ACC1 module axis
if entering at an offset
28
Scattering Parameter Calculationfor the 2x7
Superstructure

• TESLA Collaboration Meeting
• INFN Frascati May 26-28, 2003
• Karsten Rothemund, Dirk Hecht, Ulla van Rienen

29
2x7-Superstructure
Images I.Ibendorf
30
HOM-Coupler (HOM 2 HOM 3)
31
7 Cell TESLA Cavity
S../dB
Plot MWS, simulation MAFIA, 2D, time domain
S../dB
S../dB
f/GHz
f1.5-3.0 GHz
f/GHz
32
CSC-Computation
Calculation of overall S-matrix open ports beam
pipe, 3x HOM-, 1x Input-coupler 1500 values
computed in 1.5-3 GHz frequency range shown
here 2.46-2.58 GHz (3rd dipole passband) 481
frequency-points interpolation
S../dB
S-values of 7-cell cavity
f/GHz
33
Results
Coupling between HOM1 and HOM2 to beam pipe modes
S../dB
upstream beam pipe
HOM2
S../dB
HOM1
f/GHz
downstream beam pipe
f/GHz
34
Summary

• S-parameter of 2x7 TESLA-Superstructure have
  been
• calculated (an open structure) with CSC
• 5 modes have been considered in the structure
• S-parameter of subsections were computed with
• CST-MicrowaveStudioTM (coupler sections, 3D)
• MAFIA (TESLA cavity, 2D-rz-geometry)
• analytically (shifting planes, rotation)
• some exemplary coupling parameters have been
• presented
• computation times for S-parameters of
  subsections
• in order of days
• additional computation times whole structure
  then in
• the order of minutes
• parameter tuning (e.g. rotation angles,
  distances)
• possible

35
Start-to-End Simulationsfor theTESLA LC

• A Status ReportNick WalkerDESY

TESLA collaboration Meeting, Frascati, 26-28th
May 2003
36
Ballistic Alignment
62
37
New Simulations usingPLACET and MERLIN

• 14 quads per bin (7 cells, Df 7p/3)
• RMS Errors
• quad offsets 300 mm
• cavity offsets 300 mm
• cavity tilts 300 mrad
• BPM offsets 200 mm
• BPM resolution 10 mm
• CM offsets 200 mm
• initial beam jitter 1sy (10 mm)
• New transverse wakefield included(30 reduction
  from TDR)Zagorodnov and Weiland, PAC2003

wrt CM axis
38
Ballistic Alignment

• Less sensitive to
• model errors
• beam jitter

average over 100 seeds
39
Ballistic Alignment
We can tune out linear ltydgt and ltydgt correlation
using bumps or dispersion correction in BDS
average over 100 seeds
40
Beam-Beam Issues
optimise beam-beam offset and angle
OK for static effect
D. Schulte. PAC03, RPAB004
41
Simulating the Dynamic Effect
IP FFBK

• Realistic simulated bunches at IP
• linac (PLACET, D.Schulte)
• BDS (MERLIN, N. Walker)
• IP (GUINEAPIG, D. Schulte)
• FFBK (SIMULINK, G. White)
• bunch trains simulated with realistic errors,
  including ground motion and vibration

All bolted together within a MATLAB framework
by Glen White (QMC)
42
Simulating the Dynamic Effect
IP beam angle
IP beam offset
43
Simulating the Dynamic Effect
2?1034 cm-2s-1
Only 1 seed need to run many seeds to gain
statistics!
44
NEW DESIGN OF THE TESLA INTERACTION REGION WITH
l  5 m

• O. Napoly, J. Payet CEA/DSM/DAPNIA/SACM

• Advantages from the detector point-of-view
• Larger forward acceptance at low angles
• Final doublet moved out of the calorimeter
• ? less e.m. showers in the detector
• Lighter Tungsten-mask and simpler support

45
NLC-like Optics
46
Simulating the Extraction Line

• Part of the extraction line included in BRAHMS
• Shadow
• Distance from IP 45m
• 2m long
• 5mm thick
• 7mm vertical distance from nominal beam (156
  µrad)
• Copper
• Septum Blade
• Distance from IP 47m
• 16m long
• 5mm thick
• 7mm vertical distance from nominal beam
• Copper

47
Realistic Beam

• Shadow
• Average deposited power 15 kW
• Septum blade
• Average deposited power 80 W