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Conceptual and Detailed Design of the NMX Beam Geometry Conditioning System

Granlund, Niklas LU (2016) In ISRN LUTFD2/TFHF-16/5212-SE(1-79) FHL820 20161
Solid Mechanics
Abstract
The European Spallation Source ERIC is a new neutron spallation source being built in Lund, Sweden, with NMX as one of the pioneer instruments. NMX is a Quasi-Laue single crystal neutron diffractometer for the investigation of large biological molecules. Wavelength, size and divergence of the neutron beam reaching the sample have to be controlled to properly match the different experimental needs. The wavelengths are selected using rotating disk choppers. Size and divergence of the neutron beam at the sample position are controlled by the Beam Geometry Conditioning System (BGCS) installed in proximity of the end station.

The purpose of the project is to perform the concept design and development of the Beam Geometry Conditioning System... (More)
The European Spallation Source ERIC is a new neutron spallation source being built in Lund, Sweden, with NMX as one of the pioneer instruments. NMX is a Quasi-Laue single crystal neutron diffractometer for the investigation of large biological molecules. Wavelength, size and divergence of the neutron beam reaching the sample have to be controlled to properly match the different experimental needs. The wavelengths are selected using rotating disk choppers. Size and divergence of the neutron beam at the sample position are controlled by the Beam Geometry Conditioning System (BGCS) installed in proximity of the end station.

The purpose of the project is to perform the concept design and development of the Beam Geometry Conditioning System for NMX, to optimize the neutronic performance of the system. The BGCS requires a motorized Pinhole Aperture that is not commercially available. As the Pinhole Aperture is in close proximity to the sample the requirements on the design are rigorous. The footprint of the system and its interaction with neutrons scattered by the sample should be minimized, along with the background noise in terms of beam halo and gamma radiation.

The development of the design has been carried out according to the design process defined by the ESS standard presented in the document Design Process and Control (ESS-0002411). This standard defines the required activities, different roles in the project and who is responsible for each activity. The design process is divided into three main phases, the concept/plan phase, the initial design phase and the detailed design phase. Each phase has to be reviewed and approved before the design may enter the following phase.

The BGCS is broken down into subsystems, individually designed to be assembled to the complete system. The main subsystems are the Collimation System, the Support Tables and the Vacuum System. The focus of the project is the development of the Collimation System, consisting of the Beam Defining Apertures and the Cleanup Apertures. The design has been performed from the basic architecture of the system, the concept design of the BGCS up to the detail design of the Pinhole Aperture.

The main component of this project is the Pinhole Aperture. The design of this system has been evaluated using the concept scoring method, to find the most feasible solution. The result of the concept selection is that the Pinhole Aperture shall consist of a rotating arm that places an absorbing cartridge in line with the neutron beam. The cartridge has a fixed aperture, defining the beam size. To change the aperture size the arm rotates to place the active cartridge in a carousel. The carousel stores cartridges with different aperture sizes, keeping them out of the neutron beam. The desired aperture size is selected by rotating the carousel to place the corresponding cartridge at the arm. The arm grabs the cartridge using magnets and the arm rotates back to place the new cartridge in line with the neutron beam.

There are three main benefits of this system design. The primary benefit is that it is possible to place the aperture close to the sample, which is the most important scientific property as it reduces the beam halo. The second benefit is that specific aperture sizes and shapes may be achieved by manufacturing cartridges matching the needs of the experiment. The last benefit is that the system is easily adjusted for future changes of the requirements. There are many uncertainties regarding which materials to use and the design of adjacent equipment. The system has been validated using Monte Carlo simulations performed with the software McStas. (Less)
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author
Granlund, Niklas LU
supervisor
organization
course
FHL820 20161
year
type
H2 - Master's Degree (Two Years)
subject
keywords
ESS, NMX, Collimation system, Neutron, Beam geometry
publication/series
ISRN LUTFD2/TFHF-16/5212-SE(1-79)
report number
TFHF-5212
language
English
id
8885637
date added to LUP
2016-06-29 10:22:13
date last changed
2016-06-29 10:22:13
@misc{8885637,
  abstract     = {The European Spallation Source ERIC is a new neutron spallation source being built in Lund, Sweden, with NMX as one of the pioneer instruments. NMX is a Quasi-Laue single crystal neutron diffractometer for the investigation of large biological molecules. Wavelength, size and divergence of the neutron beam reaching the sample have to be controlled to properly match the different experimental needs. The wavelengths are selected using rotating disk choppers. Size and divergence of the neutron beam at the sample position are controlled by the Beam Geometry Conditioning System (BGCS) installed in proximity of the end station. 

The purpose of the project is to perform the concept design and development of the Beam Geometry Conditioning System for NMX, to optimize the neutronic performance of the system. The BGCS requires a motorized Pinhole Aperture that is not commercially available. As the Pinhole Aperture is in close proximity to the sample the requirements on the design are rigorous. The footprint of the system and its interaction with neutrons scattered by the sample should be minimized, along with the background noise in terms of beam halo and gamma radiation. 

The development of the design has been carried out according to the design process defined by the ESS standard presented in the document Design Process and Control (ESS-0002411). This standard defines the required activities, different roles in the project and who is responsible for each activity. The design process is divided into three main phases, the concept/plan phase, the initial design phase and the detailed design phase. Each phase has to be reviewed and approved before the design may enter the following phase. 

The BGCS is broken down into subsystems, individually designed to be assembled to the complete system. The main subsystems are the Collimation System, the Support Tables and the Vacuum System. The focus of the project is the development of the Collimation System, consisting of the Beam Defining Apertures and the Cleanup Apertures. The design has been performed from the basic architecture of the system, the concept design of the BGCS up to the detail design of the Pinhole Aperture. 

The main component of this project is the Pinhole Aperture. The design of this system has been evaluated using the concept scoring method, to find the most feasible solution. The result of the concept selection is that the Pinhole Aperture shall consist of a rotating arm that places an absorbing cartridge in line with the neutron beam. The cartridge has a fixed aperture, defining the beam size. To change the aperture size the arm rotates to place the active cartridge in a carousel. The carousel stores cartridges with different aperture sizes, keeping them out of the neutron beam. The desired aperture size is selected by rotating the carousel to place the corresponding cartridge at the arm. The arm grabs the cartridge using magnets and the arm rotates back to place the new cartridge in line with the neutron beam. 

There are three main benefits of this system design. The primary benefit is that it is possible to place the aperture close to the sample, which is the most important scientific property as it reduces the beam halo. The second benefit is that specific aperture sizes and shapes may be achieved by manufacturing cartridges matching the needs of the experiment. The last benefit is that the system is easily adjusted for future changes of the requirements. There are many uncertainties regarding which materials to use and the design of adjacent equipment. The system has been validated using Monte Carlo simulations performed with the software McStas.},
  author       = {Granlund, Niklas},
  keyword      = {ESS,NMX,Collimation system,Neutron,Beam geometry},
  language     = {eng},
  note         = {Student Paper},
  series       = {ISRN LUTFD2/TFHF-16/5212-SE(1-79)},
  title        = {Conceptual and Detailed Design of the NMX Beam Geometry Conditioning System},
  year         = {2016},
}