Installation of Cavity Magnet - 20th of June 2007

This week we have installed the magnet around the cavity. This magnet will collimate and focus the electron beam exiting the accelerator cavity.

The magnet consists of an iron return joke and of hollow copper windings for water cooling. The windings are separated into nine sections. The current is connected in series through the section, while the water cooling is parallel through the section.

The Magnet is ready for installation. The bore of the magnet is large to be placed around the stainless steel container of the cavity.	For installation the stainless steel container has to be removed. The magnet will be attached to the aluminum 'manipulator'. With this support frame we can adjust the orientation and position of the magnet with respect tot the cavity.
The magnet is installed and the stainless steel container is put back into place.	Side view. You can see the bars with tubes. By turning the tubes the length can be adjusted so that the magnet orientation of position can be alterned.
The space between the magnet and stainless steel container is just a few milimeters. Just big enough manipulate the orientation and position of the magnet.	The weight of the magnet is supported by a spring. This makes the movement of the magnet much easier.

Cross Section of Accelerator Cavity

This pictures shows a cross section of the electron accelerator that will be installed.

The cavity consists of two cells: one 0.6 cell and one full cell. The design frequency is 2998.5 MHz (about 10 cm wavelength in vacuum). The RF waves are coupled in axial by the coaxial line. The RF waves are converted from rectangular to coaxial waveguide by the RF input coupler. The inner counductor is hollow to pass the UV excitation pulse and electron bunch.

An ultrashort UV pulse illuminates the cathode surface. By the photolectrical effect electrons are emitted from the copper cathode (up to 1 nC). These electrons will experience the very high acceleration field (about 100 MV/m) inside the cavity. Due to the very high field strength the bunch leving the cavity will be still very short, about 1 ps. The final electron energy is little less than 5 MeV. The required RF power is roughly 8.5 MW peak power during a few microseconds.

Special feature of this cavity (designed by the Eindhoven University of Technology) is the fact that the cells are no longer brassed together but pressed by screws. Therefore, a stainless steel container is needed for vacuum purpose. However, due to the fact that the faces of the copper parts are turned by single diamand turning machines a very large compression rate is expected between the inner and outer vacuum sections.

On the outside of the copper cavity cooling and heating facilities are designed. There are in total three seperate cooling channels: 1- integrated in the cathode part, 2- integrated in the center iris part, 3- on the RF input coupler. There are two integrated heating elements (Thermocoax): 1- on the cathode part, 2- on the iris part. Two thermocouples will measure as good as possible the local temperature of the cells. Through the back flange of the stainless steel container several feedthrough can be seen to support all those features.

The back flange of the stainless steel container contains also a bucking coil. This magnet compensates locally on the cathode surface the magnetic field generated by a big magnet around the cavity. For electron beam optical reasons the magnetic field has to be zero at the point where the electrons are generated.

Due to the cilindrical symmetrical design a magnet can be placed around the cavity to focus the electron beam exitting the cavity.

Test installation of vacuumsystem - 4th of June 2007

We have made the first test assembly of the vacuumsystem of the electron accelerator.

The cavity consists of two vacuum sections:

1. inner part, which are the cells of the cavity that will be pumped to a pressure below 10^-9 mbar by a Varian iongetter pump of type VacIon 150.
2. outer part, which is the space between the copper cavity and the stainless steel container that will be poump to a pressure of about 10^-6 mbar by a Varian iongetter pomp of type VacIon 20.

Outer section with RGA unit (MKS e-vision) attached.	Inner section. Directly under RF input coupler the VacIon 150 is placed on the floor. The double cross has two windows to send the UV beam to the cathode surface of the cavity.
Outer section. Via the double cross a pump by-pass is realized to the hollow inner conduction of the coaxial RF line.	Below the table the VacIon 150 is placed supported by springs instead of using a section with belows.

Electron Bunch Length Measurement

Electro-optic technique for real-time, non-destructive, single-shot measurements of femtosecond electron bunch profiles.

Explanation of measurement technique can be found at the website of Geil Berden at the FOM-institute for Plasma Physics Rijnhuizen in The Netherlands.

Announcement conference PULS'2008

The 8^th International Conference on Pulse Investigations in Chemistry, Biology and Physics PULS'2008 will be held on September 6 - 12, 2008, at Guest House of the Jagiellonian University "PRZEGORZAŁY" in Kraków, Poland.

Chairmen: Krzysztof Bobrowski (INCT) and Jerzy Lech Gębicki (IARC).

Poster NWO Spectroscopie en Theorie Meeting 2007

Poster presented at the NWO Spectroscopie en Theorie Meeting 2007:

Abstract and Presentation Miller Conference 2007

You can find my abstract and presentation of the Miller Conference 2007:

Highest RF peak power - 29th of May

Today we reached the highest peak power of RF. We measured 6.8 MW of RF. We hope to increase this soon to 10 MW by tuning all the parameters.

RF pulse from 2157A Klystron - 25th of May

In the figure you see the RF pulse (2998.5 MHz) produced by the 2157A Klystron. The modulator (ScandiNova AB) was operated at 165 kV, 4.9 us FWHM and 63 Hz. This is at full power level of 6.3 kW average power.

We have driven the input of the klystron at a low power (estimated at 2.5 W peak power, which is a tenth of the optimal power).

The output level measured by the RF diode detectors corresponds to 2.5 MW peak power. This corresponds to a small signal gain of +60 dB.

High Power RF Test - 23th of May

We have performed the first high power RF tests in May.

The RF setup is orginized in the following way:
- The output of the RF source, Phase-Locked Loop (PLL) Synchroniser, is fed to the 100-W continuous RF amplifier, MAL tld..
- Inside the PLL a RF switch is integrated at the output, so that we can produce a low power (13 dBm) RF pulse of tens of microsecond in duration.
- The MAL amplifier (type AM82-3S-45-50R) has a small signal gain of 41 dB and has a output maximum of 50.2 dBm.
- The output of the MAL amplifier is fed to the input of the Klystron Tube. The klystron tube has a small signal gain of 57 dB.
- At the output of the Klystron Tube the waveguide section (WR284) is mounted, which contains a circulator with load (Ferrite SC3-118), bi-directional coupler and RF pressure window (CPI VWX-1053) at the accelerator cavity.
- To the bi-directional coupler RF diode detectors (Agilent 423B) are connected to monitor the forward and reflected RF power.

In this test phase the RF pressure window is replaced by a reflection plate, so that all the RF power is dissipated in the RF load on the circulator.

In the control room we have placed all the measurement equipment: two puls generators to supply the trigger pulse for the modulator and RF switch inside the PLL Synchronizer. The signals are displayed on a oscilloscoop.

For the computer in the control room the modulator can be controlled and all the operating parameters can be monitored.

Upper: PLL Synchronizer, Lower: MAL RF Amplifier	N-type Coax cable connected to RF input of Klystron Tube.
Bi-directional coupler in waveguide section. RF diode detectors connected to forward and backward outputs.	Trigger signal generation and signal analyzing in control room.
Control computer in control room.	Red warning light indicates accelerator operation.