Accelerator Alignment Lab
Mandate: The lab is responsible for precision geometrical survey and alignment for accelerator machines and their beamlines at RRCAT. The team ensures alignment by survey of the machines/beamlines time to time.
For synchrotron beamlines the team does measurements for installation and alignment of beamline components w.r.t. its origin and direction in global coordinate system of the machine. After installation is completed the team does measurements during commissioning and solving the problem of not getting beam for different reason.
Apart from this, operation and maintenance (O&M) of pneumatic system for Indus Accelerator Complex, O&M of air washer units for Power conditioning system of Indus-2 and O&M of material handling devices for Indus machines are also done by the team. Pneumatic system and air-washer units are round-the-clock running systems.
- Survey & Alignment
- Alignment procedures
- Instruments and software
- Calibration Facility
- Team members
Survey & Alignment
Survey and alignment team is responsible for precision alignment of accelerator components for accelerator machines and positional relationship among accelerator machines of RRCAT namely Indus-1, Indus-2, microtronand Booster Synchrotron and synchrotron radiation beamlines on Indus-I & II. Apart from this, they also do the precision measurements for other accelerator machines in RRCAT like free electron laser system, Industrial accelerators and their beamline etc. They are also responsible for precision metrology of various large components and assemblies used in accelerators and experimental stations wherever conventional measurement techniques do not work.
Tight tolerances on alignment of accelerators components in their global coordinate system pose a challenge to the survey and alignment team. It demands control over the various sources of errors, use of precision measuring instruments, their proper calibrations, adopting proper survey techniques, accurate measurements and a robust data analysis.
Survey and alignment procedure adopted for different machines varies depending upon their shapes and sizes. The Booster Synchrotron and Indus-I machines are relatively smaller in size so, these machines were aligned using online coordinate determination system based on angle measurements and without use of control networks. However, Indus-2, which has ~ 172.4 m circumference required a network of control points to cover the entire machine for controlling the overall shape and size of the machine. Redundant measurements and least square adjustment to achieve best linear unbiased estimate of coordinates for the control points and ring components has been the approach for computation of misalignment of components and deformation of the machine.
Instruments and software
There are precision measuring instruments being used for survey and alignment like total stations, laser tracker, Distinvar® with calibrated invar wire, Laser Interferometer as distance standard etc.
Levelling and elevation: Wild N-3 optical level, Hydrostatic levelling system for online monitoring the elevation change.
An in-house developed software is used for 2-dimensional measurements (planimetric) for survey data collection and their statistical treatment like least square adjustment or alignment error analysis and used the same for on-line coordinate measurements, stake out and resection. Data analysis works like curve fittings, coordinate transformations, etc. were also done in the same software. Vertical measurements and tilt around beam path which are very stringent in accelerator machines were measured, analysed and treated separately. Commercially available softwares were used single or multiple theodolite modes for online 3D-coordinate measurements and analysis whenever needed.
In order to ensure the accuracy of distance measurements by precision distance meters, they are calibrated with distance measured by laser interferometer as standard. A 30 meter long calibration bench has been setup for this purpose. Calibration files are prepared and used for online correction of distances measured at site.
Publications of Survey and Alignment
- Construction and Alignment Experience of Indus-1 SRS in CAT, IWAA 1995, P.K. Nema, R.K. Sahu, Vijendra Prasad et al.
- Review of Alignment Activities for Indus-1 & 2 at CAT, IWAA 1999, P.K. Nema, R.K. Sahu, Vijendra Prasad et al.
- Methodology for Survey & Alignment of Indus-2, InPAC-2003, R.K. Sahu, Vijendra Prasad et al.
- Survey Network Adjustment Programs for adjustment and analysis of alignment data, InPAC-2003, Vijendra Prasad.
- Survey, data adjustment and accuracy computation of Indus-2 alignment control networks, InPAC-2005, Vijendra Prasad, R.K.Sahu et al.
- Precise Survey and Alignment of Synchrotron Radiation Source Indus-2, APAC07, Vijendra Prasad, R.K.Sahu et al.
- Distance calibration at Alignment Lab RRCAT, InPAC-2009, R.K. Sahu, Vijendra Prasad et al.
- Effect of long accurate scales on the accuracy of angle based coordinate determination systems, InPAC2018, Vikas, R.K. Sahu
- Installation of Hydrostatic Levelling System in Indus-2 and Its Preliminary Results, InPAC-2019, Vikas, P.K. Sharma et al
Team members of Survey and Alignment:
- Rajesh Kumar Sahu
- Dinesh Barapatre
- Jagdish Kumar Parate
- Jai Singh
- C. S. Yadawa
- Pankaj Kumar Sharma
- Dhoble Vinay Wasudevrao
- Jasminkumar Dineshbhai Zolpara
- Rajendra Mehar
- Ram Swaroop Saini
- Ramprasad Girdhari
- Sanat Kar