Synchrotron Utilization Section
Beamline Instrumentation
BCIL is involved in the design and implementation of beamline instruments which are common to most of the beamlines resulting in uniformity across the beamlines. Major beamline instrumentation developed is as follows:
Major Features:
- Scanning wire monitor
- Slit System controllers
- Pneumatic valve controllers
- Baking controllers for getting Ultra High Vacuum
- Low current (sub-nano ampere) electronics
- Precision multi-axis motion control systems for beamline optics
1. Scanning Wire Monitor
In scanning wire monitor, a gold coated tungsten wire of 100 µm thickness, stretched between a fork shaped machinable glass ceramic holder, is scanned vertically perpendicular to the direction of propagation of photon beam by using a precisely controlled stepper motor. The photo-electron current generated in the wire is measured by pico-ammeter.
The Graphical user interface (GUI) shown in figure 1 of SWM is developed using LabVIEW. The GUI provides an online plot of wire current versuswire position which gives the undulator radiation profile. The peak current and respective wire position gives the beam position. The wire current and position readings are logged in a spreadsheet for further analysis.
Figure 1: Graphical User Interface of SWM
The photoelectric current profiles measured using SWM for U1 and U2 undulators for different pole gaps are shown in figure 2 and figure 3 respectively.
Figure 2: Radiation profile measurement at undulator U1
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Figure 3: Radiation profile measurement at undulator U2
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The wire scans have helped in understanding the behavior of the undulator with the variation in pole gap, profile and position of the photon beam coming out from the undulator as well as upstream and downstream bending magnets. The radiation profiles observed using SWMs have also helped in estimating the effective aperture available in the dipole chamber for the passage of SR beam from undulator.
2. Slit System Controller
Most of the beamlines have 4-blade water cooled entrance slit and 2-blade exit slit for defining the x-ray beam aperture. Slit systems have stepper based linear actuators with independent motion. The slit controller has following functions:Micro-stepping, Homing, Encoder Interface, End of travel limit switches, drive brakes, RS485 PC interface. Figure 4 shows the GUI of 4-blade slit system developed in LabVIEW.
Figure 4: GUI of 4-blade slit system
3. Pneumatic gate valve controller
- Independent control of 4-pneumatic valves
- LOCAL/REMOTE/LOCK mode of operation
- Hardwired relay based interlocks
Figure 5: 4-channel pneumatic gate valve controller
4. Baking Controller
- For baking of UHV systems
- PID controller with and without Ramp/Soak profiles
- Control of 4 heating tapes each of 1 KW
- Standalone operation as well as PC interface for data logging
Figure 6: Baking controller
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