Vacuum

Storage Ring

Several new vacuum vessels were installed in the Storage Ring in 1999. The most striking item is the in-vacuum undulator which was successfully installed and commissioned during winter 1998/1999. The design of its vacuum system has proven to be reliable. Even after we were forced to vent it due to the failure of some contact fingers placed nearby, it regained a sufficiently high vacuum to allow the ID11 beamline to take beam almost immediately.

Insertion Device Chambers

A number of two and five metre long undulator chambers (made of copper plated stainless steel without pumping) of 10 mm vertical size (8 mm inner aperture) have been installed in the ring. They have undergone a number of different vacuum treatments, ex situ and in situ bake-outs but they have been found to suffer from lack of conductance and pumping speed. The main problem has been a high level of bremsstrahlung radiation in the beamline hutches and tunnel roof.

NEG-Coated Insertion Device Chambers

Based on some synchrotron radiation (SR) induced desorption measurements performed on D31, and in collaboration with CERN, we have manufactured a 5 m-long, 15 mm-high (11 mm inner aperture) extruded aluminium NEG-coated chamber. The geometry of the extrusion was chosen so that it can replace any existing 15 mm-high ID chamber in the ring. Installed and conditioned on the ID31 straight section, the indication is that the NEG-coating develops a pumping action and at the same time reduces the outgassing due to SR, confirming the many measurements performed on samples irradiated with electrons at CERN. Moreover, the bremsstrahlung radiation measured in the experimental hutch of ID31 is five times less than that of a fully conditioned 10 mm chamber (8 mm inner aperture), a comforting sign that we are proceeding in the right direction. A graph showing the conditioning of the chamber is given in Figure 142. It compares the bremsstrahlung level produced downstream of this new NEG coated aluminium vessel to those of a stainless steel vessel (devoid of pumping) and of an APS type aluminium vessel equipped with distributed NEG pumping.

Contact Fingers

A programme of characterisation and study of several contact finger assemblies was carried out. This was done on a dedicated test stand installed on the ID8 straight section. Using the instrumentation installed there (two infra-red sensors, two visible-light cameras, thermocouples and vacuum gauges) made it possible to identify the cause of the severe damage which had been noticed earlier, at several locations around the ring. We also tested a prototype designed by the SOLEIL project team and adopted, with modifications, by the Swiss Light Source project. We will soon install a prototype we have designed at the ESRF.

Safety

During 1999, much of the effort of the Radiation Protection group went into the preparation of the application of the Euratom Directive 96/29. Indeed, from May 2000 onwards, new radiation protection rules must be applied. In particular, these rules stipulate that the radiation limits for non-exposed people are divided by a factor of five (from 5 mSv/year down to 1 mSv/year), and that the quality factor for neutrons is increased from 10 to 20. The ESRF Radiation Protection policy is based on the fact that nobody working at the ESRF should be classified as a radiation worker. In other words, radiation levels everywhere around the accelerators and in the Experimental Hall should be below the limits for non-exposed workers. The ESRF will continue to maintain this policy after May 2000.

Detailed radiation measurements were carried out by the Safety Group to quantify the radiation levels outside the Storage Ring tunnel associated with electron losses. These measurements have shown that, depending on the location of the obstacle for the electron beam, dose profiles outside the tunnel are observed, which peak either near the middle of the long straight section, or at the beginning of the achromat. The results also showed that the neutron dose largely dominates the photon dose. Therefore an active radiation monitoring system has been installed, based on 64 (bubble) neutron monitors - i.e. 2 per cell - which are placed on the Storage Ring tunnel roof, at those points where the radiation levels are maximum. These monitors will be interlocked to the injector in such a way that the total effective dose, integrated over four hours, will nowhere exceed the corresponding maximum level for non-exposed workers, i.e. 2 µSv per 4 hours. This radiation monitoring system, combined with the creation of restricted areas around the injection zone, will allow dose levels to be maintained below the limits for non-exposed workers everywhere around the storage ring.

Concerning the beamlines, the limiting factor comes from the scattered radiation due to bremsstrahlung. All Optics Hutches have been reinforced with typically 2 cm of lead. At the same time, radiation measurements have been taken extensively using the Safety Group's test beamline ID31 to quantify the new 5 metre long insertion device vessels. At present the new NEG-coated aluminium 11 mm internal ID-vessel is being monitored. The first results show a net decrease in radiation levels, when compared to a standard 8 mm internal stainless steel ESRF ID-vessel, which indicates a much more efficient pumping inside the vessel.

Control System

In 1999 the Machine Control System underwent some major developments such as the upgrade of the 2nd RF transmitter and the full redesign of the Front-end control. The general computing infrastructure has been completed by the installation of a wireless Ethernet link in the technical gallery allowing a portable PC to access the machine network. This installation will be extended in 2000 for the SR tunnel.

Control System Infrastructure

One major concern in system administration was the preparation of the year 2000 transition. It generated a lot of work in investigation and patching of all Unix machines, OS9 crates and PCs.

Modernisation of the System

In 1999, we began preparations for a major modernisation of the hardware and software of the control system for the next five years. Along these lines we started the design of a new control software named "TANGO". In accordance with the latest distributed software techniques, we have also started the necessary developments to replace OS9 by Linux on the VME crates. Beside we are in the process of selecting the new hardware platform based on PCI buses, which will replace VME in the next few years.

Alignment and Geodesy

After investigation, the TDA5000 motorised theodolite with automatic target recognition (ATR) was chosen as the new survey tool to be used for a complete machine survey without a substantial loss in precision. It will enable us to significantly reduce the time required to perform the machine survey during the shutdown (compared to the distinvar/ecartometer pair, used until now).