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

2 11/18/2021

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.

11/18/20213

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

4 11/18/2021

Delivery Ring in the MARS Model

Global Frame MAD-X frame

S (m)MARS geometry in OpenGL ROOT viewer

5 11/18/2021

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).

6 11/18/2021

7

Septum 1

11/18/2021

CAD modelMARS geometry

Lambertson Model

8 11/18/2021

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

9 11/18/2021

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

10 11/18/2021

SQC Quadrupole Aperture

Drawing Number 8000-MB-170858

Implementation in MARS

Information provided by Jim Morgan

11 11/18/2021

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:

12 11/18/2021

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.

13 11/18/2021

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.

14 11/18/2021

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

15 11/18/2021

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

16 11/18/2021

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

11/18/202117

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.

18 11/18/2021

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.

19 11/18/2021