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Development of a DC Beam Model for the First Prototype of the ESS Virtual Machine

Bolling, Benjamin LU (2019) FYSM30 20191
Nuclear physics
Department of Physics
Abstract
The European Spallation Source is currently under construction in Lund, Sweden. Consisting of a linear accelerator delivering an unprecedented 5 MW proton beam to the spallation source, i.e. a rotating Tungsten disk, it will deliver high-flux neutron beams to multiple beamlines at which scientific experiments will be conducted in many scientific disciplines.

To simulate the proton beam and for creating accelerator physics applications, scripts and services, the open source multi-purpose accelerator physics software platform OpenXAL is used. It is based on a pure Java open source development environment, which thus far has been used with an ellipsoidal (bunched) beam to account for space charge effects. The virtual machine (VM) for the... (More)
The European Spallation Source is currently under construction in Lund, Sweden. Consisting of a linear accelerator delivering an unprecedented 5 MW proton beam to the spallation source, i.e. a rotating Tungsten disk, it will deliver high-flux neutron beams to multiple beamlines at which scientific experiments will be conducted in many scientific disciplines.

To simulate the proton beam and for creating accelerator physics applications, scripts and services, the open source multi-purpose accelerator physics software platform OpenXAL is used. It is based on a pure Java open source development environment, which thus far has been used with an ellipsoidal (bunched) beam to account for space charge effects. The virtual machine (VM) for the ESS Low Energy Beam Transport (LEBT) section would profit from having a properly derived continuous (DC) beam model as the beam travelling through the LEBT is DC, and the space charge effect has a strong impact on a low-energy beam.

Thus, in this thesis, a DC beam has been derived, implemented in the OpenXAL and compared against other simulation codes. The results from these comparisons were consistent, suggesting that the deriva- tion and implementation have been properly executed. After the good results from the comparisons, a first prototype of the ESS VM GUI was developed. It covers some basic functionalities and is able to simulate a DC and a bunched beam, and visualize the trajectory of the beam and its envelope. (Less)
Popular Abstract
A spallation source generally begins with a high-powered proton linear accelerator (Linac), which delivers a high-powered proton beam and smashes it into a neutron-dense target. The high-energy protons of the beam release neutrons from the neutron-rich atoms in the target via intra-nuclear interactions, which is a simple description of the spallation process.

The higher the power of the delivered proton beam is, the more neutrons are released resulting in a higher neutron current. A high current of neutrons is desirable in spallation source facilities, such as the European Spallation Source (ESS) currently under construction in Lund, Sweden. ESS can be considered as a gigantic microscope, which uses the high-current neutron beam to... (More)
A spallation source generally begins with a high-powered proton linear accelerator (Linac), which delivers a high-powered proton beam and smashes it into a neutron-dense target. The high-energy protons of the beam release neutrons from the neutron-rich atoms in the target via intra-nuclear interactions, which is a simple description of the spallation process.

The higher the power of the delivered proton beam is, the more neutrons are released resulting in a higher neutron current. A high current of neutrons is desirable in spallation source facilities, such as the European Spallation Source (ESS) currently under construction in Lund, Sweden. ESS can be considered as a gigantic microscope, which uses the high-current neutron beam to probe deep within and reveal the complex molecular structures of the samples to be investigated. There is a huge scientific and industrial interest in ESS, at which a proton beam with currently unprecedented power will be produced.

A proton beam has to begin somewhere. At ESS, it begins in an ion source in which a continuous beam of protons is generated. The continuous beam then enters the first part of the Linac, which is the low energy beam transport (LEBT) section. In the LEBT, the beam is continuous and has low energy. Particles with the same charge feel a repulsive force between one another (the Coulomb force). In a beam, many particles with the same charge travel together. The collective repulsive force results in an increase of the beam size, which is referred to as defocusing of the beam due the space charge force. The defocusing is similar to the increase of a lit-up area originating from a conventional flashlight.

Due to the fact that the low-energy beam in LEBT is non-relativistic, it experiences a stronger space charge force. Therefore, it is important to properly account for the space charge effect. The previous beam model used for beam simulations at ESS was a bunched beam, and the main difference is that the continuous beam has no longitudinal structure whilst the bunched beam has. Thus, the space charge force needs to be treated differently for the two beam types. Before this work, the bunched beam was manipulated to resemble a continuous beam by using very long bunches. In this work, the continuous beam model is derived and implemented in the model used to simulate the beam at ESS.

Comparing with the results from another accelerator software’s simulation suggests that the deriva- tion and implementation were properly executed. Thus, as a third and last part of this project, a first prototype of a graphical user interface for the ESS virtual machine (VM) was created. The VM can be described as a virtual copy of the real machine (accelerator), with which a user can interact in similar way as with the real machine. It has the option of choosing which sections are to be simulated, and which beam model to be used.

In this project, the derivation of a new beam model was performed, implemented and successfully tested and included in the first ESS VM GUI prototype. (Less)
Popular Abstract (Swedish)
En spallationskälla börjar generellt med en kraftig linjär protonaccelerator, som skickar en högenergisk protonstråle rakt in i ett neutrontätt mål. Strålens högenergiska protoner frigör neutroner från de neutronrika atomerna i målet via intra-nukleära interaktioner, vilket är själva spalleringsprocessen.

Desto högre effekt den levererade protonstrålen har, desto fler neutroner frigörs. Därmed resulterar en kraftig linjär protonaccelerator i att en hög ström av neutroner kan produceras genom spallering, vilket är önskvärt vid en spallationskälla som Europeiska Spallationskällan (från engelska ’European Spallation Source’, ESS) som för närvarande byggs i Lund. ESS kan betraktas som ett gigantiskt mikroskop, som använder neutronstrålar... (More)
En spallationskälla börjar generellt med en kraftig linjär protonaccelerator, som skickar en högenergisk protonstråle rakt in i ett neutrontätt mål. Strålens högenergiska protoner frigör neutroner från de neutronrika atomerna i målet via intra-nukleära interaktioner, vilket är själva spalleringsprocessen.

Desto högre effekt den levererade protonstrålen har, desto fler neutroner frigörs. Därmed resulterar en kraftig linjär protonaccelerator i att en hög ström av neutroner kan produceras genom spallering, vilket är önskvärt vid en spallationskälla som Europeiska Spallationskällan (från engelska ’European Spallation Source’, ESS) som för närvarande byggs i Lund. ESS kan betraktas som ett gigantiskt mikroskop, som använder neutronstrålar med hög ström för att dyka djupt in i och avslöja komplexa molekylstrukturer hos prover som ska undersökas. Därmed finns ett stort vetenskapligt och industriellt intresse för ESS, där en protonstråle med aldrig tidigare skådad kraft kommer att produceras.

En protonstråle måste skapas någonstans. Vid ESS börjar den i en jonkälla, som genererar en kontinuerlig stråle av protoner. Den kontinuerliga strålen går sedan in i den första delen av acceleratorn, vilket är en sektion för låg-energisk stråltransport (LEBT från engelskans ’low energy beam transport’). I LEBT-sektionen är strålen kontinuerlig och har låg energi.

Partiklar med lika laddning känner en repulsiv kraft mellan varandra (Coulomb-kraften). I en stråle färdas många partiklar med lika laddning tillsammans. Den kollektiva repulsiva kraften resulterar i en ökning av strålstorleken, något som kallas för defokusering av strålen på grund av den så kallade rymdladdningskraften. Defokuseringen kan liknas vid ökningen av lysarean från en vanlig ficklampa ju längre ifrån ficklampan man kommer.

Den lågenergiska strålen i LEBT är icke-relativistisk och påverkas därför mycket rymdladdningskraften. Därmed är det viktigt att under simuleringar på korrekt sätt ta hänsyn till just rymdladdningskraften. Den tidigare simuleringsmodellen hos ESS tog enbart i beaktande en strålklunga.

Den stora skillnaden mellan strålmodellerna är att den kontinuerliga strålen har ingen longitudinal struktur medan en strålklunga har det. Därmed måste rymdladdningskraften hanteras på olika sätt för de två olika stråltyperna. Innan detta arbetet fanns enbart en modell för en stråle som bestod av strålklungor, vilket är den vanligaste typen av partikelstrålar hos dagens partikelacceleratorer. För att kunna simulera en kontinuerlig stråle så manipulerades tidigare strålklunge-modellen till att bestå av väldigt långa strålklungor. I detta arbetet utvecklas den kontinuerliga strålmodellen på så sätt att den kan implementeras i strålsimuleringssystemet som används hos ESS.

Jämförelser av resultat från simuleringar gjorda med den nya strålmodellen och från ett annat acceleratorsimuleringsprogram tyder på att kontinuerliga strålmodellen har utvecklats och implementerats korrekt. Därmed, som en tredje och sista del av detta projektet, så skapades en första prototyp av ett grafiskt användargränssnitt och simuleringsprogram för ESS virtuella maskin (VM). En VM kan beskrivas som en virtuell kopia av den riktiga partikelaccelerator som man kan interagera med på samma sätt som om det vore den riktiga maskinen. I programmet finns bland annat möjligheten att välja vilken eller vilka acceleratorsektioner som ska simuleras och med vilken strålmodell.

Sammanfattningsvis kan detta projektet sammanfattas med att en ny strålmodell utvecklats, implementerats och testats med goda resultat. Strålmodellen har även inkluderats i första prototypen av ESS:s virtuella maskin. (Less)
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author
Bolling, Benjamin LU
supervisor
organization
course
FYSM30 20191
year
type
H1 - Master's Degree (One Year)
subject
keywords
Particle, Accelerator, Beam, Physics, Science, Virtual Machine, Virtual, Machine
language
English
id
8980539
date added to LUP
2019-06-10 09:47:59
date last changed
2019-06-10 09:47:59
@misc{8980539,
  abstract     = {The European Spallation Source is currently under construction in Lund, Sweden. Consisting of a linear accelerator delivering an unprecedented 5 MW proton beam to the spallation source, i.e. a rotating Tungsten disk, it will deliver high-flux neutron beams to multiple beamlines at which scientific experiments will be conducted in many scientific disciplines.

To simulate the proton beam and for creating accelerator physics applications, scripts and services, the open source multi-purpose accelerator physics software platform OpenXAL is used. It is based on a pure Java open source development environment, which thus far has been used with an ellipsoidal (bunched) beam to account for space charge effects. The virtual machine (VM) for the ESS Low Energy Beam Transport (LEBT) section would profit from having a properly derived continuous (DC) beam model as the beam travelling through the LEBT is DC, and the space charge effect has a strong impact on a low-energy beam.

Thus, in this thesis, a DC beam has been derived, implemented in the OpenXAL and compared against other simulation codes. The results from these comparisons were consistent, suggesting that the deriva- tion and implementation have been properly executed. After the good results from the comparisons, a first prototype of the ESS VM GUI was developed. It covers some basic functionalities and is able to simulate a DC and a bunched beam, and visualize the trajectory of the beam and its envelope.},
  author       = {Bolling, Benjamin},
  keyword      = {Particle,Accelerator,Beam,Physics,Science,Virtual Machine,Virtual,Machine},
  language     = {eng},
  note         = {Student Paper},
  title        = {Development of a DC Beam Model for the First Prototype of the ESS Virtual Machine},
  year         = {2019},
}