RF Cavity of CIS

Xiaoying Pang

Mar. 12th, 2007

IUCF

Present Design of CIS

• 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.

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Kink region

f=100MHz, HARM=6

Kink region

f=200MHz, HARM=12

Kink region

We tried to investigate the kink

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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 somethingelse 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

• 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.

• 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

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!