RF LINAC FOR GAMMA-RAY

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15 Νοε 2013 (πριν από 3 χρόνια και 4 μήνες)

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RF LINAC FOR GAMMA
-
RAY
COMPTON SOURCES

C. Vaccarezza on behalf of european collaboration

OUTLINE


Gamma Ray Compton Sources


New generation source requirements


ELI
-
NP: the European proposal



a S
-
C
-
band
solution :



the reference WP



the C
-
band structures



the layout



the lattice error sensitivity

HBEB 2013
,

San Juan Mar, Puerto Rico |
March

25
-
28, 2013

2

Gamma
-
Ray Compton sources

Thanks

to

the

extremely

advanced

characteristics
:

energy,tunability
,

mono
-
chromaticity
,

collimation,

brilliance
,

time

rapidity
,

polarizability

etc
.

the

new

generation

of

Compton

Sources

will

play

a

critical

role

for

advanced

applications

in
:


Nuclear resonance fluorescence


Nuclear photonics:

(
γ
-
p) (
γ
-
n) reactions


Medical applications: new medical isotopes production


M
aterial studies


Radioactive waste management and isotope identification


High brilliance Neutron sources

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

3

New generation
γ
-
source:

High Phase Space density electron beams vs Lasers


Bright


Mono
-
chromatic


High
Spectral
Flux


Tunable


Highly Polarized


Photon energy

1
-
20 MeV

Spectral density

> 10
4

ph/sec.eV

Bandwith (rms)

<0.3%

#

photons/sec within
FWHM bdw.

0.5
÷
1.5 10
9


Linear Polarization

>95 %

HBEB 2013
,

San Juan Mar, Puerto Rico |
March

25
-
28, 2013

4

The electron
-
photon collider approach:

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

The rate of emitted photons is given by:



where:


leading to:






𝛾
=

𝜎
𝑇


=

𝐿

𝑒
2
𝜋
𝜎
𝑥
2
+
𝑤
0
2
4



Laser

e
-


𝛾
𝑠 𝑐

1
=
4
.
1
×
10
8

𝐿
𝐽

𝑝

𝑅𝐹

𝑅𝐹


𝐿

𝜎
𝑥
2

+
1
4
𝑤
0
2

1
+
𝑐
𝜎
𝑡

4
𝜎
𝑥
2

5

Within the desired bandwith:

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

Δ

𝛾

𝛾

𝜗
4
+
4



2
+

𝑛
𝜎
𝑥
4
+


𝐿

𝐿
2
+

2

𝐿
2
𝜋
𝑤
0
4
+
𝑎
0𝑝
2
3

1
+
𝑎
0𝑝
2
2

2

collimation

system

e
-

beam

Laser system

A

simple

model

by

L
.

Serafini,

V
.

Petrillo

predicts

:


















/
5
.
1


2
within
sec
ph
scattered
N
N
bw
6

L.
Serafini

Spectral density SPD: a key
parameter

HBEB 2013, San Juan Mar, Puerto Rico |March 25
-
28, 2013











2
0
2
2
2
2
2
2
0
2
2
2
0
2
4
1
4
2
3
4
0
2
2
4
2
4

2
)
(
8

10
67
.
1
w
c
w
x
a
w
M
x
n
RF
RF
L
x
t
z
p
L
L
L
n
f
Q
U
SPD



















































f
RF
=
repetition rate

n
RF
=
bunches per RF pulse

U
L
=
Laser pulse energy (
J
)

Q

=
el. bunch charge (
pC
)

h

=
laser photon energy=2.4
eV

f

=
collision angle

x
=
e
-

beam focal rms spot size in
mm

w
0

= laser focal spot size in
mm


For the considered bandwith

𝜈
𝛾
𝜈
𝛾







𝑆 
𝑝ℎ
𝑠



𝑁
𝛾
𝑏𝑤
2𝜋
ℎ𝜋

𝜈
𝛾

7

Analytical
model vs. classical/quantum
simulation

V. Petrillo

CAIN (quantum


MonteCarlo)

Run by I.Chaichovska

and A. Variola

TSST (classical)

Developed by

P. Tomassini

Comp_Cross (quantum


semianalytical)

Developed by V.Petrillo

Number of

photons

bandwidth

HBEB 2013, San Juan Mar, Puerto Rico |March 25
-
28, 2013

8

ELI
-
NP: a new generation
γ
-
ray source

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

Photon

energy

1
-
20
MeV

Spectral

Density


> 10
4
ph/sec.eV

Bandwidth

(rms)


0.3
%

#

photons

per

shot

within

FWHM

bdw
.

1.0
-
4.0
.
10
5

#

photons/sec

within

FWHM

bdw
.

2.0
-
8.0
.
10
8

Source

rms

size

10
-

30
µm

Source

rms

divergence

25
-
250
µrad

Peak

Brilliance

(
N
ph
/sec
.
mm
2
mrad
2
.
0
.
1
%
)

10
22

-

10
24

Radiation

pulse

length

(rms,

psec
)

0.7
-
1.5

Linear

Polarization

> 99
%

Macro

rep
.

rate

100
Hz

#

of

pulses

per

macropulse

31

Pulse
-
to
-
pulse

separation


16
nsec

9

ELI
-
NP: the
F
-
I
-
UK

European
proposal

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

European Collaboration for
the proposal of the gamma
-
ray source:


Italy: INFN,Sapienza


France: IN2P3, Univ. Paris Sud


UK: ASTeC/STFC

~ 80 collaborators elaborating the
CDR/TDR

10

ELI
-
NP requirements:

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

11

State of the
art

Compact

S
-
band
Photoinjector

+

C
-
band linac

+

=

A r.t. RF
linac
vs

pulsed
laser source

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

Electron

beam

parameter

at

IP

Energy

(MeV)

180
-
750

Bunch

charge

(
pC
)

25
-
400

Bunch

length

(
µm
)

100
-
400

ε
n
_
x,y

(mm
-
mrad)

0.2
-
0.6

Bunch

Energy

spread

(
%
)

0.04
-
0.1

Focal

spot

size

(µm
)

15
-
30

#

bunches

in

the

train


31

Bunch

separation

(nsec)


16

energy

variation

along

the

train

0.1 %

Energy

jitter

shot
-
to
-
shot

0.1 %

Emittance

dilution

due

to

beam

breakup

< 10%

Time

arrival

jitter

(psec)

< 0.5

Pointing

jitter

(

m
)

1




Yb
:
Yag


Collision

Laser

Low
Energy
Interaction

High Energy
Interaction

Pulse

energy

(J)

0.2

0.5

Wavelength

(eV)

2.4

2.4

FWHM

pulse

length

(ps)

2
-
4

2
-
4

Repetition

Rate

(Hz)

100

100

M
2

1.2

1.2

Focal

spot

size

w
0

(µm
)

> 25

> 25

Bandwidth

(rms)

0.05 %

0.05 %

Pointing

Stability

(µrad
)

1

1

Sinchronization

to

an

ext
.

clock

< 1 psec

< 1 psec

Pulse

energy

stability

1 %

1 %





12




Advantages:


Moderate
risk (state of art RF gun, reduced
multibunch operation problems respect to higher
frequencies
, low
compression factor<3)


Economic


Compact
(the use of the C
-
band
booster
meets
the requirements on
the
available space
)



Possibility
to use SPARC as test stand


Operation criteria:



Long bunch at cathode for high phase
space
density :


Q
/

n
2
>
10
3

pC/(µrad)
2



Short
exit bunch (280 µm) for low
energy spread
(~0.05%)

The hybrid scheme for the Linac:

WP
ref

from the photoinjector
(Tstep
tracking
)

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

14

Egun=120 MV/m

E(S1)=E(S2)=21 MV/m

Q=250 pC

C. Ronsivalle

C
-
band structures

HBEB 2013, San Juan Mar, Puerto Rico |March 25
-
28, 2013

15

D. Alesini

Central cells

HBEB 2013, San Juan Mar, Puerto Rico |March 25
-
28, 2013

16

Mitigation of multibunch effect with
damped structure

HBEB 2013, San Juan Mar, Puerto Rico |March 25
-
28, 2013

17

D. Alesini

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

18

The machine layout

ELI
-
NP
infrastructure

N. Bliss

Linac & Transfer lines

19

HBEB 2013, San Juan Mar, Puerto Rico |March 25
-
28, 2013

Low energy

High Energy

SB
-
Transverse beam size and
distribution (Elegant tracking)

20

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

Low energy

High energy



WPref_SB
-
energy spread & current

HBEB 2013, San Juan Mar, Puerto Rico |March 25
-
28, 2013

21



Wake on
Δ
x=500
µ
m

22

HBEB 2013, San Juan Mar, Puerto Rico |March 25
-
28, 2013

Wake res Q
11000

Wake res Q
100

M. Migliorati

Wake on
Δ
x=500
µ
m

23

HBEB 2013, San Juan Mar, Puerto Rico |March 25
-
28, 2013

SB

Wake res Q
100

Lattice error sensitivity:

Error

value

RFCW

12

QUAD

28

DIP

4

Δ
x

80 µm

X

X

X

Δ
y

㠰₵m

X

X

X

Δ
V

300 kV

X

-

-

Δ
Φ

1
°

X

-

-

Δ
k

㕸㄰
-
4

fs

-

X

-

Δ


1x10
-
3

fs

-

X

The Latin Hypercube:


138 Variables (12*4+28*3+4*3)


-
1.0

Δ
u
/
u


1.0


100 machine runnings


The applied
Δ
x,y affects all the elements at
the same time like a real machine


Δ
x and
Δ
y are applied together


For each sample machine an Elegant input
lattice is written with the corresponding errors


The sample machine is runned


The all results are read and plotted

Ex. 10 machines
Δ
u
/
u
distribution:

Δ
V=
±

300 kV




Δ
Φ
= 1
°

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

27





Δ
x
=
±

80

m

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

28







Δ
k/k
max
=
±

5.0E
-
4



Δ
B/B
max
=
±

1.0E
-
3

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

29





All the contributions applied

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

30

Conclusions

HBEB 2013
,

San Juan Mar, Puerto Rico |March 25
-
28, 2013

31


A C
-
band RF linac has been presented based on
the requirements of the new generation gamma
-
ray
source in the framework of the ELI
-
NP project:


The key parameters have been described together with
the main aspects of the proposed solution


A lattice sensitivity study has been presented that even
if not exhaustive anyway shows acceptable probability
margin for the linac routine operation.