Accelerator Physics and Design
Working Group
Summary 2/2
O. Napoly
Frascati, 28 Maggio 2003
CEBAF Energy Recovery Experiment
Michael Tiefenback
• GeV scale Energy Recovery demonstration. – Testing the
potential of ERLs
– Demonstration of high final-to-injection energy ratios 20:1 and 50:1
– Optimized beam transport in large scale recirculating
linacs (320 SC cavities) - RF steering and skew field
compensation for accelerated/decelerated beams
56MeV injection
56MeV
556MeV
1L21
1056MeV
deceleration
56MeV
l/2 phase delay chicane
1056MeV
acceleration
556MeV
2L21
56MeV
Frascati, 28 Maggio 2003
556MeV
deceleration
556MeV
CEBAF Energy Recovery Experiment
Michael Tiefenback
rf power measurement - selected cavity at the end of South Linac
Gradient Modulator Drive Signals (SL20 Cavity 8)
0.15
Volts (mV)
0.10
0.05
0.00
-0.05
with ER
without ER
-0.10
Graph Courtesy C. Tennant
0
100
200
300
Time (s)
Standard arc BPMs go dead with ER beam:
- BPM signal at RF fundamental
- Decelerated beam is λ/2 delayed from primary beam
signals destructively interfere in BPM antennae
Frascati, 28 Maggio 2003
400
CEBAF Energy Recovery Experiment
Michael Tiefenback
current
Wire scan at 2L22: X, X-Y, Y
synchrotron
light monitor  1056 MeV Beam
500
accelerated/decelerated beams at 556 MeV
400
56 MeV Beam
300
200
100
0
0
5
10
15
20
25
30
35
Emittance measurements and Halo measurement
 Beam quality is essentially preserved (80 µA)
Frascati, 28 Maggio 2003
mm
CW Energy Recovery Linac for Next
Generation of XFELs
General Thoughts based on TESLA XFEL-TDR
TJNAF:
INFN:
DESY:
BNL:
LANL:
UCLA:
A. Bogacz
M. Ferrario, L. Serafini
D. Proch, J. Sekutowicz, S. Simrock
I. Ben-Zvi
P. Colestock
J. B. Rosenzweig
TESLA_TTF Meeting
Frascati, May 26-28, 2003
Possible layout can be very similar to the present pulsed
linac
1.8 km
~3 km
En = 10÷20 GeV
BC III : 2.50 GeV
BC II : 0.50 GeV
BC I : 0.14 GeV
RF-Gun ?
Frascati, 28 Maggio 2003
R~150 m
3xSASE 2xUndulators
Dump (0.5 MW)
• energy recovery
95%
Any combination of the bunch charge and the spacing of
bunches giving nominal current is OK
Example:
1 mA= 1 nC @ spacing 1 µs
# of 1nC bunches/s
20
1.00
15
0.75
10
0.50
5
0.25
0
0.00
10 12 14 16 18 20
En [GeV]
Frascati, 28 Maggio 2003
# bunches/s [ 1E6 ]
Beam Peak Power [MW]
Beam peak power
Conclusion
Needed R&D :
• cw RF gun
• suppression of microphonics
• more experience with the energy recovery
Total cost without experiments should be < 400
MEuros
Total AC power for Cryoplant + RF < 10 MW
But we will have :
6 x more bunches /s
very flexible time structure of the beam.
Frascati, 28 Maggio 2003
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 *
Frascati, 28 Maggio 2003
Main Questions/Concerns
• RF Focusing vs Magnetic focusing ?
• High Peak Field on Cathode ?
• Cathode Materials and QE ?
• Q degradation due to Magnetic Field ?
Frascati, 28 Maggio 2003
Measurements at room T on
a dedicated DC system
Extrapolation to
Higher Field
BNL_SCRF_CAT
0.00018
0.00016
QE
0.00014
QE
0.00012
0.0001
8 10 -5
6 10 -5
SCRF GUN
4 10 -5
2 10 -5
0
10
Measured
20
30
40
G [MV/m]
50
60
Limited by the available voltage
Frascati, 28 Maggio 2003
70
Splitting Acceleration and Focusing
Ez_[MV/m]
Bz_[T]
60
0.2
50
0.15
50 cm
30
0.1
20
0.05
10
25 cm
10 cm
0
Bz_[T]
Ez_[MV/m]
40
0
-10
• The Solenoid can be placed downstream the cavity
-0.05
-20 on the solenoid when the cavity is cold prevent any
• Switching
0
0.2
0.4
0.6
0.8
1
trapped magnetic field
z_[m]
Frascati, 28 Maggio 2003
HBUNCH.OUT
HOMDYN
Simulation
6
Q =1 nC
R =1.5 mm
L =20 ps
eth = 0.45 mm-mrad
Epeak = 60 MV/m (Gun)
Eacc = 13 MV/m (Cryo1)
B = 1.9 kG (Solenoid)
sigma_x_[mm]
5
en
[mm-mrad]
4
3
sigma_x_[mm]
enx_[um]
I = 50 A
E = 120 MeV
en = 0.6 mm-mrad
2
1
6 MeV
0
0
5
3.5 m
10
Z [m]
z_[m]
scaling laws for Q and Epeak available
Frascati, 28 Maggio 2003
15
Progress on Helical Undulator for
Polarised Positron Production
Duncan Scott
ASTeC
Daresbury Laboratory
SC Magnet Undulator Prototype

Prototype Magnet Design for 14mm period:


Beam Stay Clear 4mm
Helix Diameter 6mm
Frascati, 28 Maggio 2003
Permanent Magnet Undulator Design
• 14mm Period, 4mm Bore “Halbach” undulator
• (Klaus Halbach NIM Vol. 187, No1)
• PPM blocks create
Dipole Field
Frascati, 28 Maggio 2003
• Rotate many rings to create
Helical Field
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 107mBar
– 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
Frascati, 28 Maggio 2003
TESLA Damping Ring:
Injection/Extraction Schemes with RF Deflectors
D. Alesini, F. Marcellini
CTF3-LIKE INJECTION/EXTRACTION SCHEME
(simple scheme)
1st train
2nd train
TL
LINAC TRAIN
NB/F
VRF
Injection
Extracted
bunches
Extraction
MAIN
LINAC
Train 1
RF Defl.
Extr.
RF Defl.
inj.

DR
Train 2
 (deflection angle)
SEPTUM
TL

1)
2)
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 
Frascati, 28 Maggio 2003
 /MAX=1-cos(2/F)
MAX
*
TDR
=TL/F
Rec. factor
Extr./Inj.
bunch
3 Frequencies
 maximization of MAX
in the range [430*1/ TL 450*1/ TL] =1.276  1.335 GHz
3 distant freq.
case

3 close freq.
case
 no bunch length
MAX = 69 %
DEFLECTOR PARAMETERS (/2)
6 Deflectors (3 inj. + 3 extr.)
Defl 1  fRF1 = 433*1/ TL = 1284.87 [MHz]
Defl 2  fRF2 = 438*1/ TL = 1299.70 [MHz]
Defl 3  fRF3 = 443*1/ 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
Frascati, 28 Maggio 2003
P = 5.00 [MW]
L = 0.86 [m]
F = 64 [nsec]
n. Cells/defl = 15
FINITE BUNCH LENGTH
 z=6 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
Frascati, 28 Maggio 2003
3 Frequencies
 maximization of 1
in the range [430*1/ TL 450*1/ TL] =1.276  1.335 GHz
 bunch length z=6 mm
1 = 57 %
3 distant freq.
case

3 close freq.
case
DEFLECTOR PARAMETERS (/2)
6 Deflectors (3 inj. + 3 extr.)
Defl 1  fRF1 = 444*1/ TL = 1317.51 [MHz]
Defl 2  fRF2 = 437*1/ TL = 1296.74 [MHz]
Defl 3  fRF3 = 435*1/ 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]
P = 9 [MW]
L = 0.78 [m]
F = 58 [nsec]
n. Cells/defl = 13
Frascati, 28 Maggio 2003
P = 5.00 [MW]
L = 1.04 [m]
F = 77 [nsec]
n. Cells/defl = 18
F=100  LDR2.85 Km
 maximization of 1
3 distant freq.
in the range [430*1/ TL 450*1/ TL] =1.276  1.335 GHz
 bunch length z=2 mm
DEFLECTOR PARAMETERS (/2)
6 Deflectors (3 inj. + 3 extr.)
Defl 1  fRF1 = 447*1/ TL = 1326.41 [MHz]
Defl 2  fRF2 = 440*1/ TL = 1305.64 [MHz]
Defl 3  fRF3 = 436*1/ TL = 1293.77 [MHz]
Total beam deflection = 2.16 [mrad]
Deflection defl.1 = 0.72 [mrad]
Deflection defl.2 = 0.72 [mrad]
Frascati,
28=Maggio
2003
Deflection
defl.3
0.72 [mrad]
1 = 28 %
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
OUR EXPERIENCE WITH RF DEFLECTOR FOR CTF3
1. STUDY AND
NUMERICAL
SIMULATIONS
2. MECHANICAL
DRAWING
1st turn - 1st bunch train from linac
2nd turn
3rd turn
4th turn
3. CONSTRUCTION
Frascati, 28 Maggio 2003
4. MEASUREMENTS
MODE /2; DEFLECTION=0.5 mrad; fRF=1.3 GHz; DISK THICKNESS=11.53 mm; CELL LENGTH=57.65 mm
3.5
300
Filling time (f) [nsec]
deflector length (L) [m]
3
2.5
2
1.5
1
200
150
100
0.5
0
20
250
30
40
50
60
50
20
70
30
40
60
70
50
60
70
P=5 MW
P=9 MW
15
1
0.8
/2 MODE
kick3MHz/kicknom
Dissipated power per unit length (dP/dz) [kW/m]
@ 5 Hz, 1 ms RF pulse
50
a [mm]
a [mm]
10
0.6
0.4
Deflection
= 0.5 mrad
0.2
fRF = 01.3 GHz
5
Disk
thickness = 11.53 mm
-0.2
0
20
30
Frascati, 28 Maggio 2003
40
50
a [mm]
60
70
Cell-0.4length = 57.65 mm
20
30
40
a [mm]
Beam Position
Measurements
in TTF Cavities
G. Devanz,
O. Napoly, CEA, Gif-sur-Yvette
A. using
Gössel,Dipole
S. Schreiber,
M. Wendt,
DESY,
Hamburg
Higher
Order
Modes
Module II
Module III
ON
Beam
OFF
HOM 2
q = 3.5 nC
fb = 2.25 MHz
Tp = 780 s
Spectrum analyser
• used as aparametric
bandpass filter:
– central frequency
– resolution bandwidth
• signals in time domain
Frascati, 28 Maggio 2003
HOM 1
Agilent E8563E
spectrum analyser
GPIB
Att
10 dB
zero span
Dipole mode measurements
2 positions computed using
2 modes with the same beam
10
8
6
beam position (mm)
High gradient in cavities
(~ 20 MV/m)
 orbit is expected
to cross ACC1
module axis
if entering at an offset
4
2
0
-2 0
1
2
3
4
5
6
-4
-6
-8
-10
cavity index
Frascati, 28 Maggio 2003
7
8
9
10
Scattering Parameter Calculation
for the 2x7 Superstructure
TESLA Collaboration Meeting
INFN Frascati May 26-28, 2003
Karsten Rothemund, Dirk Hecht, Ulla van Rienen
2x7-Superstructure
7 Cell TESLA Cavity
Input-Coupler
e-
HOM-Coupler
Radius Adapter
Images: I.Ibendorf
Frascati, 28 Maggio 2003
HOM-Coupler (HOM 2 + HOM 3)
27.4 mm
HOM 3
27.4 mm
shift planes
HOM 2
rotate
Input
HOM 3
Frascati, 28 Maggio 2003
HOM 2
HOM 1
7 Cell TESLA Cavity
|S..|/dB
TE11
Plot: MWS, simulation: MAFIA, 2D, time domain
|S..|/dB
|S..|/dB
TM01
f=1.5-3.0 GHz
Frascati, 28 Maggio 2003
f/GHz
TE21
f/GHz
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
Frascati, 28 Maggio 2003
Results
Coupling between HOM1 and HOM2 to beam pipe modes
|S..|/dB
upstream beam pipe
|S..|/dB
HOM1
HOM2
f/GHz
downstream beam pipe
Frascati, 28 Maggio 2003
f/GHz
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
Frascati, 28 Maggio 2003
Start-to-End Simulations
for the
TESLA LC
A Status Report
Nick Walker
DESY
TESLA collaboration Meeting, Frascati, 26-28th May 2003
Ballistic Alignment
angle = i
quads effectively
aligned to ballistic
reference
bi q
i
ref. line
Lb
Frascati, 28 Maggio 2003
with BPM noise
62
New Simulations using
PLACET and MERLIN
•
•
•
14 quads per bin (7 cells,  = 7/3)
RMS Errors:
– quad offsets:
300 m
– cavity offsets:
300 m
– cavity tilts:
300 rad
– BPM offsets:
200 m
– BPM resolution:
10 m
– CM offsets:
200 m
– initial beam jitter: 1y (~10 m)
New transverse wakefield included
(~30% reduction from TDR)
[Zagorodnov and Weiland, PAC2003]
Frascati, 28 Maggio 2003
wrt CM axis
Ballistic Alignment
Less sensitive to
• model errors
• beam jitter
average over 100 seeds
Frascati, 28 Maggio 2003
Ballistic Alignment
We can tune out
linear <yd> and
<y’d> correlation
using bumps or
dispersion
correction in
BDS
average over 100 seeds
Frascati, 28 Maggio 2003
Beam-Beam Issues
4
3.8
off
Lang
approx.
3.6
L [1034cm-2s-1]
optimise beambeam offset and
angle
L1
3.4
3.2
OK for ‘static’
effect
3
2.8
2.6
2.4
2.2
2
20
22
24
26
ey [nm]
28 PAC03,
Maggio 2003
D. Frascati,
Schulte.
RPAB004
28
30
Simulating the Dynamic Effect
LINAC
BDS
IR
IR
BDS
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
Frascati, 28 Maggio 2003
All ‘bolted’ together
within a MATLAB
framework by
Glen White (QMC)
Simulating the Dynamic Effect
IP beam angle
Frascati, 28 Maggio 2003
IP beam offset
Simulating the Dynamic Effect
21034 cm-2s-1
Only 1 seed: need to run many seeds to gain statistics!
Frascati, 28 Maggio 2003
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
NLC-like Optics
300
b
1/2
(m
1/2
hx (m)
)
200
0,15
0,10
Beamstrahlung Dump
SF
SF
hx
b z1/2
100
0,05
SD
2
b x1/2
SF1, SD1
s (m)
0
0
Frascati, 28 Maggio 2003
100
200
300
400
0,00
500
h'x (mrad) L/L0 @ 0,4% ex (m.rad)
FFS
l* (m)
TDR
3
0.0
0.73
6.6 10-14
NLC-like
5
10.0
0.86
5.6 10-14
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
Frascati, 28 Maggio 2003
Realistic Beam
• Shadow:
Average deposited
power: ~15 kW
• Septum blade:
Average deposited
power: ~80 W
Frascati, 28 Maggio 2003