Download X. Pang

RF Cavity of CIS
Xiaoying Pang
Mar. 12th, 2007
IUCF
Present Design of CIS
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Energy=25MeV
The Lowest frequency f=16.6MHz
HARM=1(for the MPI cavity)
We can choose the right voltage to get longer life times.
The power should also be affordable.
i.e. VOLT  5kV, We can get the Touschek Life Time  2hr
If the shunt impedance of the cavity is R  2000
V2
According to
 P, P  6.25KW. We can achieve
2R
thi s by using a solid state power amplifier.
F=16.6MHz HARM=1
Kink
region
f=100MHz, HARM=6
Kink
region
f=200MHz, HARM=12
Kink
region
We tried to investigate the kink
8 2 x z s

Nr02 c
1
T 
1 dN
N dt
3
 pˆ  1


 mc  D( )
s
 1
  ( u  )
1
1

D( )    
[u   ln    ln( u   )] e
du
2
0
2
2
 (u   )

  (  x pˆ /  2 mc x ) 2  (pˆ 2 / E 4 x )  x m 2 c 6

Kinks are located in the region [0.04:0.06] [GeV]. From the above
graph we can tell,  is smooth in this region. There must be something
else responsible for this. We will investigate this in the future.
Quantum Life Time
MPI Cavity
• Wide tuning range with external quadrupole ferrite biasing (1.3MHz
to 10MHz correspond to proton energy 7MeV-200MeV)
In the ferrite materials, as the
bias current increase, the biasing
magnetic field increase, but the
effective permeability decrease.
So we can achieve resonance at different frequency and also
reduce the length of the cavity.
(This kind of scheme proposed by S. Papureanu and first adopted
at Max Planck Institute. So called MPI cavity)
Diameter of the cavity ~0.55m; Length ~0.6m
10 Philips accelerator ferrite rings:
material: 8C12; dimension
• 40 turns of windings are put on each
tip of the quadrupole
The center of the ferrite ring where the
beam pipe is located is well protected
from the biasing field due to the canceling
of the field at the center
• The outer conductor is make of copper stripes.
The inner conductor is perforated.
A fan forces air through all these air passages
to keep the ferrite and cavity cool.
• A 70mm gap between the loop magnet and
main magnet. The loop biasing magnet is
used for the input impedance matching
• RF power is coupled into the cavity by a driving port which is directly tapped to the
center conductor of the cavity. The port is a magnetic loop.
effective inductance of the cavity VS biased current
Our goal is to increase the resonace frequency but make the shunt
impedance as high as possible. So we may need to make the loaded
capacitance lower (around 100pf) or cut the length of the cavity.(Q=40)
We are trying to model this cavity. We will ultimately get more
understanding from the real experiment!