Extraction Scenarios of CIS
Zhengzheng Liu
Mar 12th, IUCF
Pulse from linac
Extracted beam
Lambertson septum
Kicker 1
Kicker2
Shut down during
extraction
Some Parameters in extraction
•
•
•
•
Extraction requirement estimation:
(1) 13 turns injection scheme (horizontal tune 1.72)
(2) 5 mm septum thickness
(3) 60 MeV injection and extraction energy
• Total energy delivered to the target in pulsed mode:
• Assuming linac current 0.5 A, inject 40ns electron beam per turn.
with 13 turn accumulation, we obtain
Q  0.5 A  40ns 13  260nC
Energy  QE  260nC  60MV  15.6 J
Accumulated beam after injection
• After multi-turn injection, we will carry out single-turn extraction.
Below is the accumulated beam at the septum right after the last
injection turn.
0.015
0.01
0.005
-0.01
0.01
-0.005
-0.01
0.02
0.03
Electrostatic kicker for extraction
The injection and extraction share the same section in the ring. Beam size
is about 50 mm. So we need to bump the closed orbit by 47 mm in order to
kick the whole beam into the septum.
x’
25mm
5mm
25mm
x
8mm
xco= 47mm
 ( s) 2
xco ( s) 
 i i cos   (s)  i 
2 sin   i 1
 k  36mrad
Closed orbit bumped for extraction
Kicker field and aperture requirement
• For extraction, kick angle  k  36.6mrad is needed for 47mm closed
orbit bump. Using electrostatic kicker:
EL
k 
c  B
and B  0.2[Tm] for 60 MeV extraction
Thus we get E L=2.2 [MV/m] [m] for 60 MeV extraction. If assume 50mm
kicker length, displacement within the kicker are:
Kicked beam
θk
beam
(1)xco
xco
 L  tan( 0.006 / 2)  1.5mmat 13th injection turn.
(2) xco
turn).
 L  tan( 0.036 / 2)  9mm at extraction (after 13th injection
kicker strength operation (60MeV, x  1.75 )
Aperture requirement for kicker 2
44mm horizontal aperture is enough for the 2nd kicker.
0.02
0.01
-0.01
13th injection turn at the entrance of the
second kicker. xco= 1.5mm.
0.01
-0.01
During extraction, kicker is
shut down, so the phase space
at the kicker location is like
0.02
Aperture requirement for kicker 1
After 12th injection turn, we shut down kicker 2. Thus, the
13th injection turn phase space at the kicker 1 entrance
requires –x aperture to be at least 26mm.
0.015
xco  9mm at the exit
0.01
0.005
-0.025
-0.02
-0.015
-0.01
-0.005
0.005
0.01
-0.005
-0.01
-0.015
-0.02
Total horizontal aperture
required : 52mm
Vertical Lambertson extraction magnet
The vertical Lambertson septum is used to extract beam vertically.
Injection
Extraction
Septum
35
1.15m
35
35
0.81m
1.15m
0.2m
We put the septum in the middle of the drift space where
 (kick  sept.)   / 2.
Bx l
z ' 
B
we choose z '  35 deflected by the septum to avoid the next element.
Septum strength and aperture
x
35
z
z
• For 25 MeV extraction,
• For 60 MeV extraction,
B  0.0834.[Tm]
B  0.2[Tm]
Bx  0.25[T ]
Bx  0.61[T ]
The beam displacement at the exit of septum is z  63mm. So, due to
the 50mm horizontal beam size, we need 50mm horizontal aperture
and 1cm vertical aperture.