frascati, 28 maggio 2003 accelerator physics and design working group summary 2/2 o. napoly

Frascati, 28 Maggio 2003

Accelerator Physics and DesignWorking Group

Summary 2/2

O. Napoly


CEBAF Energy Recovery ExperimentMichael 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

/2 phase delay chicane

1L21

2L21

56MeV 556MeV

556MeV1056MeV

556MeV1056MeV

56MeV 556MeV

deceleration

acceleration

deceleration


0.15

0.10

0.05

0.00

-0.05

-0.10

Vo

lts (

mV

)

4003002001000Time (s)

with ER without ER

Gradient Modulator Drive Signals (SL20 Cavity 8)

Graph Courtesy C. Tennant


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 λ/2 delayed from primary beam signals destructively interfere in BPM antennae



synchrotron light monitor – accelerated/decelerated beams at 556 MeV

Emittance measurements and Halo measurement Beam quality is essentially preserved (80 µA)

500

400

300

200

100

0

35 30 25 20 15 10 5 0

56 MeV Beam

Wire scan at 2L22: X, X-Y, Y

1056 MeV Beam

mm

current

CW Energy Recovery Linac for Next Generation of XFELs

General Thoughts based on TESLA XFEL-TDR

TJNAF: A. Bogacz INFN:INFN: M. Ferrario, L. SerafiniDESY:DESY: D. Proch, J. Sekutowicz, S.

SimrockBNL: I. Ben-ZviLANL: P. ColestockUCLA: J. B. Rosenzweig

TESLA_TTF Meeting Frascati, May 26-28, 2003


RF

-Gu

n

?B

C I

: 0

.14

GeV

BC

II

: 0.5

0

GeV

BC

III

: 2

.50

GeV

En

= 1

0÷

20

GeV R

~150

m

1.8 km

~3 km

Dump (0.5 MW)

3xSASE 2xUndulators

Possible layout can be very similar to the present pulsed linac

• energy recovery 95%


0.00

0.25

0.50

0.75

1.00

201816141210

En [GeV]#

bun

ches

/s [

1E6

]

0

5

10

15

20 B

eam

Pea

k Po

wer

[MW

]

# of 1nC bunches/ s

Beam peak power

Any combination of the bunch charge and the spacing of bunches giving nominal current is OK

Example: 1 mA= 1 nC @ spacing 1 µs


Conclusion

Needed R&D :• cw RF gun• suppression of microphonics• more experience with the

energy recoveryTotal cost without experiments should be < 400 MEurosTotal AC power for Cryoplant + RF < 10 MWBut we will have :

6 x more bunches /s very flexible time structure of the beam.


* TESLA Meeting - Frascati - 27 May 2003 * TESLA Meeting - Frascati - 27 May 2003 **

Towards a Towards a Superconducting High BrightnessSuperconducting High Brightness

RF PhotoinjectorRF Photoinjector

M. Ferrario, J. B. Rosenzweig, J. Sekutowicz, L. SerafiniM. Ferrario, J. B. Rosenzweig, J. Sekutowicz, L. Serafini

INFN, UCLA, DESYINFN, UCLA, DESY


Main Questions/ConcernsMain Questions/Concerns

• RF Focusing vs Magnetic RF Focusing vs Magnetic focusing ? focusing ?

• High Peak Field on Cathode ?High Peak Field on Cathode ?

• Cathode Materials and QE ?Cathode Materials and QE ?

• Q degradation due to Magnetic Q degradation due to Magnetic Field ?Field ?


2 10-5

4 10-5

6 10-5

8 10-5

0.0001

0.00012

0.00014

0.00016

0.00018

0 10 20 30 40 50 60 70

BNL_SCRF_CAT

QE

QE

G [MV/m]

SCRF GUN

Measured

Limited by the available voltageLimited by the available voltage

Measurements at room T Measurements at room T on a dedicated DC on a dedicated DC

systemsystem

Extrapolation to Extrapolation to Higher Field Higher Field


Splitting Acceleration and Splitting Acceleration and FocusingFocusing

25 cm10 cm

50 cm

• The Solenoid can be placed downstream the cavity The Solenoid can be placed downstream the cavity

• Switching on the solenoid when the cavity is cold Switching on the solenoid when the cavity is cold prevent any trapped magnetic fieldprevent any trapped magnetic field

-20

-10

0

10

20

30

40

50

60

-0.05

0

0.05

0.1

0.15

0.2

0 0.2 0.4 0.6 0.8 1

Ez_[MV/m] Bz_[T]E

z_[M

V/m

]B

z_[T

]

z_[m]


0

1

2

3

4

5

6

0 5 10 15

HBUNCH.OUT

sigma_x_[mm]enx_[um]

sig

ma

_x_

[mm

]

z_[m]

Q =1 nCQ =1 nC

R =1.5 mmR =1.5 mm

L =20 psL =20 ps

thth = 0.45 mm-mrad = 0.45 mm-mrad

EEpeakpeak = 60 MV/m (Gun) = 60 MV/m (Gun)

EEacc acc = 13 MV/m (Cryo1)= 13 MV/m (Cryo1)

B = 1.9 kG (Solenoid)B = 1.9 kG (Solenoid)

I = 50 AI = 50 A

E = 120 MeVE = 120 MeV

nn = 0.6 mm-mrad = 0.6 mm-mrad

nn

[mm-mrad][mm-mrad]

Z [m]

HOMDYN Simulation

6 MeV6 MeV

3.5 m

scaling laws for Q and Escaling laws for Q and Epeakpeak available available

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


Permanent Magnet Undulator Design

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

• Rotate many rings to create Helical Field

• PPM blocks create Dipole Field


• 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

Progress on Helical Undulator for Polarised Positron Production

TESLA Damping Ring: Injection/Extraction Schemes with RF Deflectors

D. Alesini, F. Marcellini


DR

SEPTUM

RF Defl. Extr.

RF Defl. inj.

VRF Train 1

Train 2

Injection

CTF3-LIKE INJECTION/EXTRACTION SCHEME (simple scheme)

*

TL

TDR

=TL/F

MAX

(deflection angle)

Extr./Inj. bunch

1) 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.

2) should be * depending on the ring optics and septum position. Considering a single RF frequency

/MAX=1-cos(2/F)

Extracted bunches

MAIN LINAC

Extraction

1st train 2nd train

NB/F TL

LINAC TRAIN

Rec. factor


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

P = 5.00 [MW]L = 0.86 [m]F = 64 [nsec]n. Cells/defl = 15

MAX = 69 %

3 Frequencies

maximization of MAX in the range [430*1/ TL 450*1/ TL] =1.276 1.335 GHz no bunch length

3 distant freq. case

3 close freq. case


FINITE BUNCH LENGTH

New optimization procedure:

- to increase 1

- (if possible) to reduce the RF slope over the bunch length

z=6 mm, the same 2 freq. optimized in the previous case give:

1 = 9 %

Extracted bunch

How to avoid the effect of the RF curvature on the extr. bunches







3 Frequencies

1 = 57 %

maximization of 1 in the range [430*1/ TL 450*1/ TL] =1.276 1.335 GHz

bunch length z=6 mm

3 distant freq. case

3 close freq. case


F=100 LDR2.85 Km maximization of 1

in the range [430*1/ TL 450*1/ TL] =1.276 1.335 GHz

bunch length z=2 mm






1 = 28 %

3 distant freq.


OUR EXPERIENCE WITH RF DEFLECTOR FOR CTF3

1. STUDY AND NUMERICAL SIMULATIONS

2. MECHANICAL DRAWING

3. CONSTRUCTION

4. MEASUREMENTS

1st turn - 1st bunch train from linac

2nd turn

3rd turn

4th turn


20 30 40 50 60 700

0.5

1

1.5

2

2.5

3

3.5

a [mm]

de

flect

or

len

gth

(L

) [m

]

P=5 MWP=9 MW

20 30 40 50 60 7050

100

150

200

250

300

a [mm]

Fill

ing

tim

e (

f) [n

sec]

20 30 40 50 60 700

5

10

15

a [mm]Dis

sip

ate

d p

ow

er

pe

r u

nit

len

gth

(d

P/d

z) [k

W/m

] @

5 H

z, 1

ms

RF

pu

lse

20 30 40 50 60 70-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

a [mm]

kick

3MH

z/kic

k nom

MODE /2; DEFLECTION=0.5 mrad; fRF

=1.3 GHz; DISK THICKNESS=11.53 mm; CELL LENGTH=57.65 mm

/2 MODE

Deflection = 0.5 mrad

fRF = 1.3 GHz

Disk thickness = 11.53 mm

Cell length = 57.65 mm


Module III Module II

OFF

q = 3.5 nCfb = 2.25 MHzTp = 780 s

Agilent E8563Espectrum analyser

zero span

HOM 2

HOM 1

Att10 dB

GPIB

Spectrum analyser

Beam

• used as aparametric bandpass filter:– central frequency– resolution bandwidth

• signals in time domain

ON

Beam Position Measurements in TTF Cavities using Dipole Higher Order Modes

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


Dipole mode measurements

-10

-8

-6

-4

-2

0

2

4

6

8

10

0 1 2 3 4 5 6 7 8 9 10

cavity index

bea

m p

osi

tio

n (

mm

)

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

Scattering Parameter Calculationfor the 2x7 Superstructure

TESLA Collaboration Meeting

INFN Frascati May 26-28, 2003

Karsten Rothemund, Dirk Hecht, Ulla van Rienen


2x7-Superstructure

-e

7 Cell TESLA Cavity

HOM-Coupler

Input-Coupler

Images: I.Ibendorf

Radius Adapter


HOM-Coupler (HOM 2 + HOM 3)

HOM 2

HOM 2HOM 3 HOM 1

Input

rotate

HOM 3

shift planes

27.4 mm27.4 mm


7 Cell TESLA Cavity

f=1.5-3.0 GHz

TE11

TM01

TE21

Plot: MWS, simulation: MAFIA, 2D, time domain

f/GHz

|S..|/dB

f/GHz

|S..|/dB |S..|/dB


CSC-Computation

Calculation of overall S-matrixopen 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-valuesof 7-cell cavity

f/GHz

|S..|/dB


Results

Coupling between HOM1 and HOM2 to beam pipe modes

HOM1

HOM2

downstream beam pipe

upstream beam pipe

f/GHz

|S..|/dB

f/GHz

|S..|/dB


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

Start-to-End Simulationsfor the

TESLA LC

A Status Report

Nick WalkerDESY

TESLA collaboration Meeting, Frascati, 26-28th May 2003


Ballistic Alignment

bi qi

Lb

quads effectively aligned to ballistic reference

angle = i

ref. line

with BPM noise

62


New Simulations usingPLACET 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: 1y (~10 m)

• New transverse wakefield included(~30% reduction from TDR)[Zagorodnov and Weiland, PAC2003]

wrt CM axis


Ballistic Alignment

Less sensitive to • model errors• beam jitter

average over 100 seeds


Ballistic Alignment

average over 100 seeds

We can tune out linear y and y’ correlation using bumps or dispersion correction in BDS


Beam-Beam Issues

2

2.2

2.4

2.6

2.8

3

3.2

3.4

3.6

3.8

4

20 22 24 26 28 30

L [1

034

cm-2

s-1]

y [nm ]

L1off

Langapprox.

optimise beam-beam offset and angle

OK for ‘static’ effect

D. Schulte. PAC03, RPAB004


Simulating the Dynamic Effect

Realistic simulated ‘bunches’ at IPRealistic simulated ‘bunches’ at IP– linac (PLACET, D.Schulte)linac (PLACET, D.Schulte)– BDS (MERLIN, N. Walker)BDS (MERLIN, N. Walker)– IP (GUINEAPIG, D. Schulte)IP (GUINEAPIG, D. Schulte)– FFBK (SIMULINK, G. White)FFBK (SIMULINK, G. White)

bunch trains simulated with realistic bunch trains simulated with realistic errors, including ground motion and errors, including ground motion and vibrationvibration

LINAC BDS IR BDSIR

IP FFBK

All ‘bolted’ together within a MATLAB framework by Glen White (QMC)



IP beam angle IP beam offset



21034 cm2s1

Only 1 seed: need to run many seeds to gain statistics!

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


0

100

200

300

0 100 200 300 400 500

0,00

0,05

0,10

0,15

hx

hx (m)

bx1/2

bz1/2

s (m)

b1/2 (m1/2)

SF1, SD1

SF

SD2

SF

Beamstrahlung Dump

NLC-like Optics

0.73 6.6 10-14

x (m.rad)L/L0 @ 0,4%FFS

TDR 3 0.0

l* (m) h 'x (mrad)

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


Realistic Beam

• Shadow:

Average deposited power: ~15 kW

• Septum blade:

Average deposited power: ~80 W

frascati, 28 maggio 2003 accelerator physics and design working group summary 2/2 o. napoly

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