The mover system has been published in NIM A368 (1996) 579-592, G.Bowden et al., where the detailed explanation can be found. A mover consists of 3 eccentric shafts rotated by 3 cams. The cam positions are monitored by 3 potentiometers (Pots). Reference position of mover is a midrange position, where all the Pots have about 5V. The accurate voltages are read and stored in a data base in order to set the mover at the midrange position. At the same time, relative positions to the midrange one ( 2 vertical and 1 horizontal positions) are monitored by 3 LVDTs. Therefore, there are 2 independent measurement systems of 3 positions, while the latter has been chosen for their resolution, their linearity and their ease of use at FFTB, SLAC.
The step size of x and y magnet positions is actually 300nm by the LVDT resolution of 0.18um ±0.15um and the dynamic range is ±1mm. The third setting variable is tilt. So, the three variables of x, y and tilt can be set and read at each magnets.
The control software is based on the EPICS-IOS with CAMAC modules. The basic functionality of software has been checked in this May. User interface has been made in a hurry to allow testing during the short time in may. Therefore, I would very much like to see an ATF2 display template then redo my displays accordingly.
Next plans are (1) to accommodate the floor tilt, (2) to prepare "trim" function, (3) to update constants and (4) to make displays consistent.
There are 34 c-band BPMs and 4 s-band BPMs. S-band electronics consisting 4 channels from SLAC-ESA and 6 new ones will be completed and tested by end of August, 2008. The shipping schedule will be decided.
The software system is based on EPICS infrastructure, and also it has simulated databases for development of software.
Finally, action items and discussion points were listed below;
He presented the same talk as that at the software review meeting, LAL, 18-20 June, 2008.
All the control and monitoring software were completed, which are running on linux PC with EPICS IOC. Various displays are provided at the PC. Documentations are available on SLAC wiki page at https://confluence.slac.stanford.edu/display/ATF/ATF2+Magnet+Power+Supplies .
Also, this software system has a simulation mode in the EPIC environment.
The gamma-ray detector consists of 7 CsI crystals (0.54Xo/cm), whose overall dimension is 100mm (width) x 50mm (height) x 340mm (length). It is segmented into 5 along beam line, longitudinally, where the first 4 layers are 10mm long and the 5th layer has 3 lateral segmentation with 300mm length.
The detector, i.e. gains of all 16 photomultipliers (PMTs) have been calibrated by cosmic rays as MIP particles, while they could be calibrated with gamma ray sources such as Na22 and Co60. In this calibration scheme, the high voltages of PMTs were set to higher values than those at beam tests since signals of cosmic rays are a few percent of actual ones. Therefore, actual high voltages were calculated by gain curves which have been measured with laser light .
The beam test results were shown with the GEANT4 simulation results. The signal distribution was estimated by "LW-ON" - "LW-OFF", where the latter was background.
There is a concern on this calibration method. If the gains changes, the shape of the distributions will change so that the systematic error becomes large. Therefore, we should have realtime calibration system. Two candidates were considered. First one is to use the background distribution which must be assumed to be constant. Second one is to use cosmic rays triggered with additional counters.
Participants : Tauchi, Kuroda, Okugi, Yamanaka and Oroku(WebEx)
We started the interference fringe measurement. The improvement of the fringe contrast can be seen, when using a seed laser. Position stability at the IP seems to be bad becase of laser angular jitter.
Next we plan to combine laser position measurement and fringe contrast measurement, then we will correct the position jitter at the IP.