How the Electron-TOF system was built

The Electron-TOF sytem was designed and built within a 12 month period in 1994/95. In April 1995 the chamber was delivered (built by Huntington but unfortunately with half the ports missing) to the ALS of LBNL. The parts for the E-TOF system were machined at different locations, namely the UT (Tennessee), UNLV (Nevada), Huntington (CA), D&D Machining (NV) and Magnetic Shield Corp (IL) The moment had come to see if everything would fit as designed. Total cost of the complete system was more than $200,000.-.

This picture shows the support stand for the E-TOF chamber. It is a modified blue table sitting on a self-made aluminum cart. Two ball bearings are mounted on the cart to allow for the chamber rotation.

Here we lift the chamber into the ball bearings of the support stand and tighten the chamber to the ball bearings so it won't slip out when in use. The people in the photo are (from left to right): Jon Levin, Dave Hansen, Ralf Wehlitz and Scott Whitfield. Behind the chamber is Peter Glans.

Scott and Dave are happy that the chamber is finally mounted to the support stand. In the front of the photo is the µ-metal chamber with holes for all the ports which is to be mounted next into the E-TOF chamber. The µ-metal chamber's purpose is a shield against magnetic fields (mainly from the earth) from the interaction region in the E-TOF chamber. The magnetic fields would disturb slow electrons on their way into the analyzers thereby lowering the count rates and adversely affecting the resolution.

This photo (taken by Scott Whitfield) shows Oliver Hemmers the designer of the Electron-TOF system, the photographer of the group responsible for most of the pictures shown on the XAMS web site (that's why he is not in them) and the author and web master of the XAMS web site. I made sure that all the parts of the E-TOF system were built and available on time and that the whole system was put together correctly. Here I am assembling my two newly-developed microchannel plate detectors which are mounted at the end of the analyzers. These devices measure the time of flight of electrons in the time range of 300 ns to 3ns seconds with a resolution of 200 ps.

Ralf Wehlitz helped to develop the Electron-TOF analyzers. The new lens system (designed by Oliver Hemmers) to increase the transmission for slow electrons was built and tested by him and is now in use in all our analyzers. Ralf Wehlitz is assembling the two new analyzers for our E-TOF system. The analyzers can be moved in two directions allowing for accurate alignment with the interaction region and thereby improving signal strenth, resolution and transmission.

All three analyzers are ready to go into the chamber now. They are wrapped in aluminum foil to protect them from dirt. Everything that goes into the vacuum chamber has to be kept as clean as possible otherwise it will take too long to achieve the vacuum needed to perform the experiments.

The 20" backflange was mounted onto the chamber with the help of a crane. The photo shows Scott Whitfield and our team leader Dennis Lindle.

Peter Glans and Scott Whitfield are connecting the pumps to the E-TOF system as they prepare everything for the first vacuum test and leak checks. Peter was also responsible for building and testing the gas manifold system mounted at the back of the chamber.

The chamber is pumping and ready to go to beamline 6.3.2. In front of the chamber are (left to right) Ralf Wehlitz, Scott Whitfield, Dave Hansen and Honghong Wang.

The chamber is now mounted to beamline 6.3.2 and Scott Whitfield is working on the wiring for the three analyzers.

Ralf Wehlitz is working on the oscilloscope adjusting the signals of the coincidence electronics.

Dave Hansen, Peter Glans, Scott Whitfield and Ralf Wehlitz (from left) pose outside the ALS with the t-shirts designed for our first run. In the background is the San Francisco Bay Area.

Thanks a lot for all your help in making the Electron-TOF system work!!!

After the first beamtime we had to completely disassemble the E-TOF system to ship the chamber back to the manufacturer for adding the missing ports. I called almost once a week to stress the importance of receiving the chamber at least a week before the next beamtime. We received the finished chamber after more than 3 month on a Friday afternoon (4 days before the next beamtime) with oil dripping from the inside. This caused an additional delay of 2 days because we had to wait until the following Monday to get the chamber cleaned at the LBNL (these guys took us in on Monday morning at 6:30 am as their first job - thanks a lot) before we could get started assembling it again. By Wednesday we were ready for measurements after working almost 24 hours a day - of course totally exhausted by then. The problem was that we had just 9 days of measurements left for the year and due the delay we lost 2 days which is more than 20 %.

During the last 2 years a fourth analyzer and two more microchannel plate mountings were built (one as a backup) and added to the E-TOF system. A 22" gear ring was mounted on the backflange to allow chamber rotation with a handle. The gear ring serves also as a break to prevent the chamber from rotating out of position. Two gravitational sensors were mounted on the chamber to determine the angle of rotation. We modified the support stand to simplify the chamber alignment procedures and to make it easier to move the chamber around to different beamlines in the ALS building. Scott Whitfield took the lead in designing and building a differential pumping section that is mounted at the front end of the chamber. It adopts the relatively high pressure (10^-5 hPa) in the chamber during measurements to the lower pressure of the beamline (10^-8 hPa). Burkhard Langer, a former post-doc in the group of then team member Nora Berrah, spent a lot of time to develop the data aquisition software using LabView. He also helped to adopt the software to the recently purchased coincidence electronic from Kornel Wieliczek.

In 2000 we completed analyzer 5 that will be commissioned during the beamtime in July/August 2000.

Send comments to Oliver Hemmers.

Last updated on May-31-2000.