Concept of beamline and sample chamber - 11th of June 2009

We have designed part of the beam line that will be placed behind the picosecond electron accelerator. It will consist of a view elements that have the function to illuminate the cathode surface with UV pulses, guide the electron beam to the sample and place different samples in the electron beam. All will take place in vacuum.

The samples will be placed on a big wheel so that we can test more that one sample before we have to open the sample chamer. The sample wheel can be moved with respect to the electron beam, so that the total area of the sample can be used to study the properies. The sample chamber has to laser beam lines that cross the samples at exactly the same position as the electron beam. We have the possibility to use to different wavelength regions to probe the sample, that are the VISible and the InfraRed.

Below, you will find to pictures showing the global layout. One is showing only the essential parts of the beam line and sample chamber. The other is showing the total cross section.

So, far a few components have been realized. One of them is the big sample chamber and the sample wheel. Those components are ready to be installed as soon as the RF processing is succeshully finished.

Essential components of the beam line and sample chamber: UV incoupling, steering magnets, filter wheel, beam monitor and faraday cup.

Total cross section of the accelerator, beam line and sample chamber.

Poster presented at PAC 2009 - 11th of June 2009

Here is a copy of the poster presented at the Particle Conference 2009 (PAC 2009) in May 2009 in Vancouver Canada.


All rights reserved, Copyright (c) 2009, Delft, The Netherlands

Contribution to PAC 2009 - 11th June 2009

We presented our accelerator setup as part of a shared contribution to the Particle Accelerator Conference 2009 (PAC 2009) held in May in Vancover Canada together with Eindhoven University of Technology and Pulsar Physics from The Netherlands.

Procedings will be published later. Below you can find the abstract. For more information

Design, construction and operation of the Dutch rf-photoguns

S.B. van der Geer, M.J. de Loos, W. op ‘t Root, W. Knulst, W. van Dijk, G.J.H. Brussaard, O.J. Luiten

Three different S-band rf-photoguns have been constructed by Eindhoven University of Technology in the Netherlands: A 1.5-cell, a 100 Hz 1.6-cell, and a 2.6-cell. They share a design concept that differs from the ‘standard’ BNL-gun in many aspects: Individual cells are clamped and not brazed saving valuable manufacturing time and allowing damaged parts to be replaced individually. The inner geometry employs axial incoupling, inspired by DESY, to eliminate any non-cylindrically symmetric modes. Elliptical irises, identical to a 2.6-cell design of Strathclyde University, reduce the maximum field on the irises and thereby reduce electrical breakdown problems. The manufacturing process uses single-point diamond turning based on a micrometer-precise design. The overall precision is such that the clamped cavities are spot-on resonance and have near-perfect field balance without the need for any post-production tuning. Operational performance of the three Dutch rf-photoguns will be presented.

Update on status - 11th of June 2009

The current status of the system is that we are preparing for the first RF processing procedure to train the copper cavity. A few systems have to be put into operational before we can start, such as cavity temperature control, vacuum control and RF power control.

Last year we have had many setback, such as vacuum leaks to do cracks in the soldering. All have been repared and since the end of the summer 2008 the cavity has been installed into its stainless steel container. After that, a vacuum backout session has been conducted to clean the cavity.

In September 2009 we also finished a demonstration version of the RF cavity made out of brass that has been caoted by gold. I have added a few pictures.

Side view of the RF cavity. On the left is the cathode surface and on the right the coaxial incoupling of RF power that is also the electron beam exit.

On this side you can clearly see the springs that clamp the cavity cells together and press it on the RF in coupler. You can also see the cooling channels and the thermocouples to measure the internal temperature.

On this side you can see the coaxial structure. The RF in coupler or mode transformer is connected to the cavity on this side.

Our Nano Letters article receives attention

Researchers demonstrate 'avalanche effect' in solar cells from PhysOrg.com

Researchers at TU Delft (Netherlands) and the FOM Foundation for Fundamental Research on Matter have found irrefutable proof that the so-called avalanche effect by electrons occurs in specific, very small semiconducting crystals. This physical effect could pave the way for cheap, high-output solar cells. The findings are to be published in scientific journal Nano Letters this week.

[...]

Major setbacks in RF and vacuum system - April 2008

In the beginning of 2008 we have had two major setbacks in the RF and vacuum system. Restoring these damages aquires a lot of time.

1. We broke our RF window during a vacuum backing test, when it was vacuum sealed to the RF flange on the RF input coupler using a gold O-ring.
   
   In the left picture you can see the RF input coupler (part with the copper rectangular waveguide). This part transforms the RF rectangular waveguide mode into a coaxial waveguide mode by a "door knob" mode transformer. At the end of the coaxial line the entrance iris of the cavity is positioned, so that the RF power is coupled into the cavity.
   
   Since, we use all-metal seals also the RF window was supposed to be sealed by a gold O-ring of 1 mm diameter cross section. Therefore, in the second half of 2007 the O-ring groove was adjusted. This was done at the time when the RF flange was being resoldered after the discovery of a vacuum leak in the soldering of this flange.
   
   Now, we continue using a Viton O-ring in stead of a gold one, to reduce the risk of breaking the our spare window as well. In the future, we will install a different type of RF window.
   
2. We cracked the soldering of the stainless steel flange connected to the cavity housing on the RF input coupler. This results in a big vacuum leakage.
   
   In the right picture you can the flange in which the soldering has been cracked. This flange is sealed by using a Helicoflex metal O-ring to achieve complete all-metal seals. Probably, during assembling the forces we so high on the fange that it was deforming and thereby cracking the joint between the stainless steel flange and copper part.
   
   At this moment, we are trying the repair the damage. When restored, we will use a Viton O-ring. In the future, we have to redesign the RF input coupler so that it is suitable for using metal seals.

Hopefully, we will get back on track next month by restaring the vacuum system. After a vacuum backing procedure we will start RF conditioning of the accelerator cavity.

RF input coupler installed in vacuum system. The RF window is connected to the upper RF flange of the RF input coupler.

The flange of the RF input coupler at which the inner joint was cracked when trying to assemble it to the stainless steel cavity housing using a metal O-ring.

Cavity Magnet installed and first test - 31th of October 2007

This week the Cavity Magnet is connected to its power supply and cooling water. Subsequently, the first field measurements are performed.

Xantrex XDC 30-400 HV Power Supply (12 kW)

The on-axis field maximum is reached at 0.481 T at a current of 400 A. The power consumption is about 10 kW.

More measurements are required to get the full magnetic field information. More important is the overlap of the magnetic axis with the geometrical axis of the accelerator cavity.

Items on New-Energy TV [Dutch]

Er zijn een aantal nieuwe filmpjes op New Energy TV verschenen over onderzoek naar nieuwe materialen voor zonnecellen, waar onze groep Opto-electronic Materials ook aan meewerkt:

14-10-2007
PV-research: Nederland doet weer mee
Joint Solar Programme: het volledige verslag over het fundamenteel onderzoek naar de ontwikkeling van zonnecellen
Bekijk het item »

19-09-2007
Johan Bijleveld onderzoekt plastic zonnecellen [bij TU Eindhoven]
Joint Solar Programme dl 1: plastics zijn goedkoper en prima in staat stroompjes door te geven.
Bekijk het item »

20-09-2007
Linda Aarts sleutelt aan de kleur van het licht [bij Universiteit Utrecht]
Joint Solar Programme dl 2: door met poeders het licht op een zonnecel te breken, haal je er meer stroom uit.
Bekijk het item »

21-09-2007
Joep Pijpers koerst op quantumdots [bij AMOLF in amsterdam]
Joint Solar Programme dl 3: quantumdots ketsen twee keer zoveel elektroden los uit een zonnecel = meer stroom
Bekijk het item »

Making demonstration model of accelerator cavity - 2th of October 2007

Some pictures of the demonstration model of the cavity which is in preparation.

Picture 1	Picture 2
Picture 3	Picture 4

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.