mars15-madx-ptc beam loss modeling in delivery ring during
TRANSCRIPT
Igor Tropin
TSD topical meeting
November 18, 2021
MARS15-MADX-PTC Beam Loss Modeling in Delivery Ring During Resonant Extraction
Outline
Approach & tools
MARS model of the Delivery Ring (DR): apertures, element positioning, geometry and magnetic fields
Peculiarities of beam passage through the ring at the slow extraction.
Beam loss map generation, simulation and verification
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Approach and Tools
Beam transport in the ring is simulated by means of MAD-X PTC module coupled with MARS tracking engine. MARS continues trajectories of the beam particles which leave the phase space where PTC module is applicable and takes care of particle matter interactions with accelerator component materials and magnetic fields there.
Tools uses the MAD-X input file to position the elements and define the magnetic field in the magnets.
Particle transport in machine components in presence of magnetic and electric fields is performed by means of the MARS tracker.
The full beam is represented by the extracted branch sample. To avoid tracking particles that are not likely to hit the aperture, only a
small fraction of the representative sample close to the septum foils (9% -> ) is used in the beam sample.
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Beam Model
Beam kinetic energy: 8 GeV
Spill = 43 ms
1.e12 protons in a spill
8 spills during supercycle
1 supercycle = 1.333 sec
Total beam intensity 1.e12*8/1.333 = 5.7e12 p/sec
Provided beam sample represents 9% of the total beam:0.09*5.7e12 = 5.4e11 p/s
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Delivery Ring in the MARS Model
Global Frame MAD-X frame
S (m)MARS geometry in OpenGL ROOT viewer
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Elevation view
SS20-30
SS10-60
SS40-50
Extraction section
Extraction Region as Implemented in the Model
Septum1
Septum2
Lambertson
C-magnet
q205
SQC quadrupoles
MARS model geometry in FreeCAD GDML workbench (tunnel is not shown).
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Septum 1
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CAD modelMARS geometry
Lambertson Model
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8Q24 Quad
The vacuum pipe in this magnet is circular stainless steel, the inside diameter is 7.98" and the outside diameter is 8.16".
BNL magnet, drawings are not available
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B (SDD) Dipole Aperture
The dipole body is curved, but the vacuum pipe is a straight rectangular one, made of stainless steel with outside dimensions 3.75" high by 7.34" wide and a thickness of .1054" (inside dimensions 2.07" x 6.29").
Drawing B000-ME-169882
MARS implementation
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SQC Quadrupole Aperture
Drawing Number 8000-MB-170858
Implementation in MARS
Information provided by Jim Morgan
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Drift Default Aperture
-“In general, most drifts are a circular vacuum tube with outside dimension 5.625" and .0625" wall thickness. However, in the 10 straight section between Q606 and Q106 locations, there are circular vacuum tubes with outside dimension 4" and .0625" wall thickness. There are many exceptions, especially around instrumentation and special pipes at injection or extraction”
According to Jim Morgan:
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Beam particle tracks in Injection region for 4 Turns
1000 tracks, 5 turns, E > 0.5GeV
1e4
1c1c
2
2
33
Source
1e,4
1c, 2, 3
Using resonant optics, the particles of the provided sample are directed into the c-magnet at the beginning of the first and fourth revolution.The numbers shown in red – turn number, e- extracted beam, c- circulating one.
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Beam Sample Fraction in Aperture of Lambertson,Q205, C-magnet
Turn No.
Lambertson Entrance Q205 quadrupole Extracted Circulated Entrance Exit
1 Extracted 0.4750.922 0.920
0.427
Circulating 0.488 0.487
2 Extracted 5.01e-30.458 0.457
1.40e-3
Circulating 0.455 0.455
3 Extracted 3.27e-50.4541 0.4541
7.81e-6
Circulating 0.4541 0.4541
4 Extracted 0.4010.4016 0.4016
0.399
Circulating 0.0028 0.0023
5 Extracted 1.30e-37.73e-4 7.70e-4
7.69e-5
Circulating 6.6e-4 6.6e-4
82.7% of the beam sample extracted to c-magnet => 17.3% of particles are lost.
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Beam Losses at Injection
4.1%
0.6%
3.7%
0.2%
8.6% of particles are lost in injection region at the beginning of first turn(equivalent to 0.8% of the beam loss)
Beam direction
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The loss point is determined as the location of the particle hitting the beam aperture during 5 turns. This assumes normalization to the full beam intensity of 9e10 protons.This is a basis for collimation system design, location choice and collimator parameters.
Calculated Beam Loss Distribution
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SS10-60 SS50-40 SS30SS20, injection
Arc20-10 Arc60-50 Arc40-30
Beam Losses in Lambertson, Q205 and Downstream Drift
Turn No. Lost Fraction%
1 4.1
2 0.2
3 0
4 0.2
5 0.1
Turn No. Lost Fraction%
1 0.2
2 0.1
3 0.
4 0.
5 3.e-4
Turn No. Lost Fraction%
1 0.6
2 0.06
3 0
4 0.03
5 0.0033
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Partial Beam Losses
42.7% of beam sample is extracted into C-magnet after the first passage of particles through separators. 40% are extracted at the beginning of the 4-th turn.
Total loss fraction for slow extraction is 17.3% of the initial sample, equivalent to the 1.6% of the beam loss
8.6 % lost on the first passage through the region between separator and C-magnet (0.8% of total beam loss)
Losses in the ring excluding injection region are about 6% (0.54%) which occurs mostly on the third revolution after injection.
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SummaryFrom Beam Loss Maps through Collimators to Minimal Impact on Components and Environment
Further perfection of the MADX/PTC/MARS system.
Identification of the “hot” regions in the lattice (Delivery Ring specifically).
Starting from those spots, design and implementation of the two-stage collimation system via thorough MARS simulations and optimization of the collimation efficiency.
MARS15 calculations and mitigation of the radiation loads on the lattice elements, prompt dose on the berm, residual dose rates in the collimation components and air activation in those regions as well as ground water activation outside the tunnel walls.
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