Operating two target stations at ISIS requires higher beam currents from the synchrotron and has led to a programme of detailed studies and upgrades. A key part of this is improving the beam diagnostic systems to better; monitor, control and ultimately improve the accelerators performance.
The amount of beam that the synchrotron can accelerate is limited by the proportion that escapes the accelerating fields and hits the edge of the vacuum pipe. This lost beam can cause synchrotron components to become radioactive which makes hands-on maintenance problematic. Monitoring loss levels is therefore crucial to the successful operation of the facility. Measuring beam profiles and positions allows accelerator physicists to understand how beam loss occurs.
A LabVIEW application has been produced to receive and display data from the 39 beam loss monitors around the circumference of the ISIS synchrotron, 2 multi-channel profile monitors which measure real time transverse beam profiles and 25 split-electrode beam position monitors.
The LabVIEW system synchronises and acquires 10ms of data from each monitor electrode, subtracts signal baseline, identifies peaks and troughs, and calculates the beam position for each revolution of the beam.
Beam loss can now be identified on the individual monitors at any time in the accelerator cycle. One of its key features is an ActiveX 3D graph control which can display losses at 4 times the previous spatial resolution.
The LabVIEW/PXI system has made the process of simultaneously collecting and analysing large amounts of data from each of the individual monitors relatively simple.
Another advantage to the system development is that instead of having to physically oversee an experiment from the control room, users are now able to log-on to the system anywhere in ISIS, with updates of results happening live. Different users may simultaneously access the data and analyse it in different ways across the ISIS network.
Alongside this, a profile simulator has been developed which will allow all electronics and computer hardware and software to be tested even in the absence of a proton beam.
In order to ensure LabVIEW is used to it’s full advantage, Sarah has recently set up a LabVIEW User group for RAL, so that scientists involved in these experiments can come together to share their experiences and expertise.
As a result of all the developments ISIS staff have made in improving accelerator performance, Sunday 27th September 2009 saw ISIS beat the record for highest average 24 hour beam current - a record set back in 1997. This is an incredible achievement.
Bryan Jones and Sarah Whitehead, ISIS - Science and Technology Facilities Council, UK
Research date: November 2009
Read the paper in full