RF systems for ThomX

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15 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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15
th

European Synchrotron Light Source

Radio
-
Frequency Meeting



5
-

6 October, 2011

ESRF, Grenoble





RF systems for ThomX

P. Marchand
-

Synchrotron SOLEIL

The
ThomX

Project

Compact source of hard X
-
rays (40


90 keV)

Flux of up 10
13

photons / sec, generated by Compton Back Scattering

(CBS : collisions between e
-

bunches and laser pulses


ω

dif

~ 4

γ
2

ω

laser

)

Funding

of 12 M


for Phase 1 : building of a prototype


晥f獩扩汩t礠灲潯f

†† †††† †††† ††††


偨P獥s㈠㨠楮摵獴物慬楺慴a潮

Work supported by the EQUIPEX program from the Research Ministry,

Région

Ile de France, CNRS
-
IN2P3 and University of Paris
-
Sud

Contributions from

LAL
-
Orsay

CNRS
-
IN2P3, SOLEIL, CELIA Bordeaux,
ESRF, C2RMF
-
CNRS, UDIL CNRS, INSERM Grenoble, Thales TED,

Institute Neel Grenoble

LAL
-
Orsay

& SOLEIL

in charge of the accelerator complex, housed inside the
former DCI building on the university site in
Orsay

(~ 5 km from SOLEIL)

Applications


-

Medical sciences (imaging + therapy)

-

Cultural heritage sciences (Louvre Museum, for instance)

Compactness

for accommodation in hospitals and museums

ThomX accelerator complex

Injection
of a single e
-

bunch (20 mA), which collides at each turn with
laser pulses at the IP, inside the FP optical resonator


X 牡祳 晲潭o䍂C

䍂匠


晡獴f摥杲慤慴楯d 潦⁴桥oe
-

beam quality


獴潲慧攠s潲 縠㈰~





䥮橥捴楯渠牡瑥映㔰r䡺

⡡(瑥t ㈰2

, 數瑲慣瑩潮 瑯t䉄…B湥n 楮i散瑩潮e

SR optics

:
4
-
fold
symmetry
Double Bend
Achromat



FP
optical

cavity

Interaction
Region

10 m

7 m

The LINAC Injector

Photocathode RF gun

:



Replica of the CERN
-
CTF3 gun, built by LAL



E
c

= 100 MV/m with 10 MW



Mg cathode

(Q up to 1 nC)



Laser :
l

㴠㈶㘠湭
,
E ~ 100 µJ,
s
t

~ 5 ps


Accelerating structure

:



LIL type (4.5 m long) AS, spare from SOLEIL



P = 10 (20) MW



䔠㴠㔰⠷〩䵥

剆偯睥P⁳畲捥





35 MW TH 2100 klystron from Thales



Solid state modulator (3 µs, 50 Hz)



Power splitting :

10 MW


䝵渠

†† †††† †††† ††††
㈰ 䵗




䕸灥捴敤E扥慭b灥牦p牭慮捥r⡐䅒䵅䱁M



E ~ 50 MeV (max 70)



s
E
/E < 0.4 %



e
n

~ 5
p

浭⹭牡搠

2.5 cell 3 GHz gun

HV modulator


Klystron

RF system of the
Storage Ring

At 50 MeV

,

U
rad

~ 2 eV / turn


P
beam

( I
b

= 20 mA ) ~ 0



No power to be delivered to the beam (

s

= 0)



RF system only generates V
RF

for suitable longit. acceptance



Selected RF frequency


㔰〠䵈5

-

V
RF

= 500 kV


ㄠ獩湧汥l捥汬c捡c楴i


P
RF

(dis) ~ 35 kW

-

Availability of power sources & other RF components

-

Reasonable equipment size

-

Z
hom




睩汬⁤楣瑡瑥i瑨攠c
桯楣攠潦i捡c楴i⁤敳楧n

Good compromise

SR RF parameters


U
rad

~ 0


t
damping

( ~ 1 s ) >>
t
storage

( ~ 20
ms

)

To preserve the beam quality


䥮獴慢楬i瑹t杲潷瑨o瑩浥

,
t
i

> 20
ms

HOM impedances and
instability thresholds

Longitudinal



䡏䴠楮ir敳潮慮捥Ⱐ
t
i
l

= 2 Q
s

E/e / (
a


o

R
s

f
m
)

R
s

.
f
m

(HOM) natural : 0.1
-

1 M


⸠䝈.



t
i
l

~ 10 µs !!

Transverse



䡏䴠楮ir敳潮慮捥Ⱐ
t
i
t

= 2 E/e / (
b
T

f
rev

I
o

R
T
)

R
T

(HOM) natural : 1
-

10 M


⼠/



t
i
t

~ 10 µs !!

In both, longitudinal and transverse cases,

damping of Z
hom

by a few 10
3

is required !!

(more critical than in 3
rd

generation LS


砠㄰
)

Cures to HOM impedances

1) De
-
Qing of the HOM (HOM couplers)


愠晥f‱0
2

-

10
3




乯琠敮潵杨… 捵浢敲獯浥s敱畩e浥湴n慲潵湤⁴桥n捡c楴i

«

DAMPY

»
cavity

-

ALBA

PEP
-
2 cavity (LBNL)

2) HOM tuning


偲敶敮琠r敳潮o湴⁥硣楴慴n潮o批⁴桥b扥慭

Cures to HOM impedances


T
w

±

0.1
°
C

Power coupler



L
cav


Plunger


ELETTRA cavity with its 3 tuning means


-

Temperature control of
f
HOM



-


L
cav

(mech. deformation)



f
o



-

Movable plunger on the equator


1 single cavity


~ No beam loading


Small circumference

Well suited to

HOM tuning


Beam spectrum lines :
d
f

㴠ㄸ⁍=z


HOM resonance BW : a few 10 kHz



f
HOM

(tuning) : a few MHz




R
s

(

f

㴠=⤠⼠
R
s

(

f

⤠㴠⬠⠲儠

f

/

f )
2




A 晥眠㄰
3

to 10
4



佫⁦潲 周潭X


t
l
= 20 ms

l
b
o
s
I
e
E
Q
t
a
.
.
/
2
ELETTRA cavity L
-
HOM spectrum (9 modes) over the 18 MHz base band

Ok

Ok

Ok

Ok

Ok

HOM Spectrum

RF power source

At 500 MHz


䭬K獴s潮猬o⁉佔猬s
卯S楤i却慴a 䅭灬楦楥牳
卓r)


35 kW SSA of the SOLEIL Booster

147 modules of 330 W @ 352 MHz

~ 35 000 runing hours over 6 years


Operational availability of 100 %


Minor pbs on 5 modules only


without impact on the operation

H = 2.50 m

,


=㈠m

SOLEIL


technology


-

Well proven (6 years op.)


-

No HV


-

Modularity


r敤畮摡湣d


-



V
RF

= 500 kV, using 1 ELETTRA cavity


P
RF
(dis) = 35 kW




For ThomX, make it at

500 MHz

April 2010 :
the
SOLEIL

-

LNLS team

in Campinas
-
Brazil,

after successful tests of the amplifiers

SOLEIL
-

LNLS collaboration

Two amplifiers of

50 kW @ 476 MHz for the LNLS storage ring

with components designed by SOLEIL (RF modules of 400 W)

LNLS 50 kW RF plants

The two 50 kW SSA have run satisfactorily on the LNLS SR for ~ 1 year

SOLEIL R&D’s with SSA


6
th

generation transistors (
V
dc

= 50 V) + SOLEIL expertise


晡獴s灲潧r敳e

†† †††† †††




㌵㈠
䵈M,

P
mod

~ 700 W, G
>

20 dB,


㸠㜰%

[

Current

LR301

mod. (
V
dc

=

28 V) : P = 315

W, G = 13

dB,


㴠㘲

% @ 352 MHz

]




䡵H攠業灲潶敭敮e 㨠
P
mod

x 2.2 , better performance (G ,


Ⱐ汩湥慲楴,




& thermal stress strongly reduced (

T㨠
-

㘰6
°
䌩C


汯湧敲 汩晥f業e




Beg. 2009,
transfer of technology
agreement concluded with ELTA
-
AREVA


ESRF contract

for 7 SOLEIL type amplifiers of 150 kW (14 x 75 kW

towers)



June 2010 : A 10 kW unit (16 modules) successfully tested at SOLEIL



June 2011 : First 75 kW tower passed the acceptance tests
(


䕓剆

)




SOLEIL SSA

: Evaluate 6
th

generation transistors of lower power (~ 330 W)


from NXP &
Freescale



r数污捥e䱒L〱 w楴栠浩渮潤楦楣n瑩潮


@
352 MHz

In view of storing 500 mA using a single
cryomodule

:


Combination of two 180 kW SSA for powering one cavity


Input power coupler (P > 300 kW)
develop
t



䍅剎⽅卒䘯协F䕉E
捯汬慢
.

R & D’s with SSA

@
frequencies other than 352 MHz

Prototypes of 500 MHz module

: P = 650 W, G = 18 dB,
η

= 67 %



1 x 50 kW for ThomX



4 x 150 kW for SESAME


New features

:



Modular high efficiency 230 V
_
ac / 50 V
_
dc power converters



Option for housing the complete SSA inside a cabinet



Waveguide
-
to
-
coaxial combiner (WaCCo)


慤橵獴慢a攠捯異汩湧




偯獳楢P汩瑹t潦 浡瑣桩湧m癡物慢汥a湵浢敲 潦 浯摵汥s

Extend the technology to frequencies from FM to L band



VALVO/SOLEIL



獥琠潦s捩r捵污瑯牳r捯c敲e湧 瑨攠w桯汥 晲敱⸠牡湧攠



Prototype of 88 MHz module : P = 900 W, G = 25 dB,
η

~ 80 %



BBEF : 20 kW CW


1.3 GHz SSA for the Beijing University



Collab. Agreement under finalization with CERN for a prototype of


20 kW @ 200 MHz in anticipation of 2 x 1.6 MW

Components design is completed



䙩F獴⁴sw敲 㨠批 瑨攠敮搠潦 ㈰ㄲ

Waveguide
-
to
-
Coaxial
Combiner (WaCCo)


Two 6 inches coaxial input ports (2 x 80 kW)


ㄠ均W潵瑰畴


Replace a coaxial combiner + a coaxial
-
to
-
WG transition


Design optimization with

HFSS and Microwave Studio




A 㔰〠䵈M 灲潴潴祰攠楳⁢敩湧 晡扲楣慴敤a批 䉂䕆


Movable SC



捡渠敮獵c攠愠杯潤 浡m捨楮朠景r 摩晦敲敮琠捯湦楧畲it楯湳
w楴⁤楦i


潦 摩獳d灡瑥牳t灥p⁴潷敲 潲 摩晦d


潦 浯m畬敳u灥p 摩獳d灡瑥t


2 coaxial inputs

WG

output

d
l

ThomX LLRF system


slow loops

Compensation of slow perturbations >>
t
f
cav

= 40 µs




䍯湶敮瑩e湡n 䱌剆
晲敱略湣e, 灨p獥Ⱐ慭a汩瑵摥d汯l灳p



剥灬楣愠潦 瑨攠慣a畡氠慮慬a杵攠协䱅䥌⁤敳楧 Ⱐ慤慰瑥搠景r 㔰〠䵈M

Phase
control

500 MHz

Voltage
control


Tuner




PID

PID

Drive

3dB

Coupler

RF
SWITCH

40 kW
AMPLIFIER

CAVITY

-

+



Tuning
control

PID



Phase loop

Amplitude loop

Frequency tuning loop

V
cav

d
V

d




o


c慶


c慶




d
f

RF ON

/

OFF

Fast phase / energy oscillations


Injection errors,
d
b
i

,
d

i



Mismatch between injected bunch and RF bucket


HOM excitations


Transient beam loading


(
I
b

: 0
-

20 mA instantly)




-

d


= 8
°

(


摩癩摥搠批

G
fbk

)


-

Only first injections (
stationary
after ~ 1

s
)



Oscillations in phase & energy
@ f
s
, the synchrotron frequency


with damping time,
t
d



1

/


U
rad

d

i

d
E/E

d


d
b
i

d

i

d

(
t
)

t

Either Phase or Energy errors


偨P獥s☠䕮敲杹 潳捩汬慴楯湳 ⡱畡摲慴畲攩


t
d

~ 1 s >>
t
st

= 20 ms


縠湯 湡瑵牡氠摡浰楮朠摵物湧d
t
st


f
s

= 500 kHz >> BW
cav

= 25 kHz


摡浰楮朠瑨r潵杨 瑨攠捡c⸠業灯獳楢se



3

means for generating some damping

:


1) Longitudinal FB using an additional broad band cavity


2)
Harmonic

cavity



䱡湤L甠
摡浰楮m


3)
Direct RF FB on the main cavity


楮ir敡獥e楴猠敦晥捴楶攠BW
㸠㔰〠歈k)

e
-

bunch length : 20


30 ps rms

Laser pulse duration : 5 ps rms


Synchro e
-

/ laser


琠‼㔠灳5





㰠<
°




(

b

/

E)
inj

=


〮㔠
%⡌䥎(䌩




inj

=


8
°

(AS)

Still amplified by
mismatch & HOM

Without oscillation damping

:




䕭E瑴慮ce

杲潷瑨o

†† †


䉡搠扵湣栠b 污獥l 潶敲e慰

Loss of efficiency in the

e
-
/laser interactions @ IP

Fast phase / energy oscillations

No need for additional cavity









ω
Z
ω
G
1
ω
Z
ω
Z'




T
Δ
ω
j
s
0
e
R
G
ω
G


0
G

1
Z
Z'


With FB :


At resonance (





r
) ,







Loop delay

ThomX

: ampli
-

cavity distance ~ 10 m



吠縠ㄵ〠湳n

†††††††††


G
limit

~ 60


䉗 縠ㄮ㔠䵈M 㸾

f
s



0
x
cav
cav
G

1

BW
BW'



I
g


I
b

R
g

R
s

C

L

V
c

-

+


G

P
in

Gain limitation ( stability criterion )




ΔT
ω
2
Q
π
G

1
r
L
0


Ampli
-
cav
distance

;

Direct RF Feedback principle

Z(
ω
)

-200
-150
-100
-50
0
50
100
150
200
495.00
496.00
497.00
498.00
499.00
500.00
501.00
502.00
503.00
504.00
505.00
Phase [
deg
.]

Gain 0
Gain 44
Gain 66

T = 150 ns

-60
-50
-40
-30
-20
-10
0
495.00
496.00
497.00
498.00
499.00
500.00
501.00
502.00
503.00
504.00
505.00
Amplitude [dB]

Gain 0
Gain 44
Gain 66

吠T‱50湳

f
r
-

f
s

f
r
+ f
s

Frequency (MHz)

Frequency (MHz)

Cavity transfer function with RF FB

MO

500 MHz

Driver

RFSwitch

AMPLI 50 kW

CAVITY

Interlocks

I
b

Phase

Shifter

3 dB

RF FB + fast beam phase loop

d




Phase

comparator

BPM

90
°

G


Phase loop

(BW >
f
s
)



RF FB




cav

x

(1

+

G
o
) >
f
s





䵯摵污瑥

V
cav

at

f >
f
s

-

Phase comparison between
V
c

(PU
cav
) &
I
b

(BPM)

-

The error signal,
d


⠫(㤰
°
) controls a
phase shifter



Alternative

: Modulate the MO with
d



BW ?



G
o






RF feedback

Att

PU
cav



inj

= 10
°
,
G
o

= 50, G


㴠㔠Ⱐ

吠T‱㔰湳

Damped after 20 µs



T
_
damping = 3 µs for G


㴠㌰3⡳瑡扩b楴i業楴i

Phase / energy oscillations

with RF FB + fast phase loop

Beam
phase

Phase
control

MO

500 MHz

Voltage
control





PID

PID

PA

3dB

Coupler

RF
SWITCH

50 kW
AMPLI

CAVITY

-

+



Tuning
control

PID




3dB

G
o





Direct RF Feedback

Att

Att

Conventional system with 3 «

slow

» loops around the cavity

Frequency



Amplitude


Phase


Complete LLRF

Beam

PU

G



Tuner

A

Oscillations @ f
s

(500 kHz)





inj
, HOM, …


-

Direct RF Feedback (G ~ 50)


-

Fast beam phase loop (BW > 500 kHz)


Summary & Conclusion


1) One 500 MHz ELETTRA type cavity (HOM tuning)


2) 500 kV with

35 kW, supplied by a SOLEIL type SSA


3) LLRF : conventional system with 3 slow loops (
f
r

,

s



v
)


+ high gain RF feedback & fast phase loop (

b
)

RF system of ThomX SR

Planning

: RF equipment available for installation in ThomX
by mid
-
2013


-

Amplifier & LLRF



摥獩杮敤d☠獵灰汩s搠«

瑵牮r步k

묠批

协䱅䥌

††
-

䍡癩瑹



潮攠潦 瑨攠䕌䕔呒T 捡c楴楥猬s摥摩捡瑥搠瑯 卅十S䔬

†† †††
浡m攠慶慩污扬攠景r 周潭T 畮u楬

浩d
-
㈰ㄶ1⡶慬楤慴a潮o潮 瑨攠

†† †††
浡捨楮攠慮搠瑨敮e晡扲楣慴楯渠潦 慮潴桥h 潮攬e浯m楦楥搠潲 湯琩

Rem

: ThomX is a small machine, but quite complex and challenging,


in particular as regards to the electron beam dynamics