Physics Requirement Document (PRD) · Web viewShielding design and amounts vary for different locations around the ring and small losses at higher energy produce larger residual (c.f

PIP-II Booster CollimatorsPhysics Requirement Document (PRD)

Document number: ED0010237

Document Approval

Signatures Required Date Approved

Originator: Dave Johnson, Booster L3 Manager -

Concurrence: Alex Martinez, Integration Coordinator -

Approver: Ioanis Kourbanis, Accelerator Upgrades L2 Manager Signed in Teamcenter

Approver: Eduard Pozdeyev, Project Scientist Signed in Teamcenter

Revision History

Revision Date of Release Description of Change- 10/7/2019 Initial Release

PIP-II Booster Collimators

Page left intentionally blank for revision history.

Fermi National Accelerator Laboratory 2


Table of Contents1. Purpose................................................................................................................................4

2. Scope...................................................................................................................................4

3. Acronyms.............................................................................................................................4

4. Overview.............................................................................................................................. 4

5. Reference Documents..........................................................................................................8



1. Purpose

Physics Requirement Documents (PRDs) contain the summary parameters and configuration definitions for systems, sub-systems, and devices that impact higher-level requirements established in the PIP-II Global Requirements Document (GRD) [1]. PRDs establish a traceable link to lower-level requirements (FRSs, TRSs) that affect the PIP-II beam or machine performance. In the aggregate, the PRDs for the PIP-II Project contain the essential parameters and configuration developed through the preliminary design phase to enable completion of the PIP-II accelerator and complex design.

2. Scope

This document describes the high-level parameters for the Booster Collimators.

3. Acronyms

FRS Functional Requirements Specification

GRD Global Requirements Document

L2 WBS Level 2 System

L3 WBS Level 3 System

MEBT Medium Energy Beam Transport

PIP-II Proton Improvement Plan II Project

PRD Physics Requirements Document

TRS Technical Requirements Specification

4. Overview

The new two stage collimator to be installed in Booster utilizes thick primary collimator blades (H&H) to produce large angle scattering with two secondary collimators to intercept the scattered particles, all contained within the same monolithic device. The secondary collimators are made up of a fixed H&V aperture and an adjustable H&V aperture. The complete unit is designed to easily fit within a single Long straight section. Figure 5-1 shows the proposed transverse cross section of the collimator assembly and Figure 5-2 shows a corresponding isometric view.



Figure 5-1. Transverse cross section of the proposed two stage collimator

Figure 5-2. Isometric view of the proposed collimator layout



Radiological limits

There are two areas of concern when discussing accelerator produced radiation and radio-nuclides. One involves minimizing ionization radiation to workers outside the enclosure from prompt radiation and radiation to workers inside the radiation enclosure from residual activation of equipment. The other concerns the production of radionuclides that could enter the environmental watershed, either through “drinking water” or “surface water” contamination. These limits are determined by applicable state and federal EPA/DOE/FNAL rules/orders. The main radionuclides of concern at Fermilab are 3H and 22Na.

Table 5-1. Radiological limits

Constraint ValueDrinking water Cf < 20 piC/ml-yr 3H Cf < 0.2 piC/ml-yr 22Na

Surface water Ci < 2000 piC/ml-yr 3H Ci < 10 piC/ml-yr 22Na

Residual activation on exterior surface < 100 mRem/hr

Prompt dose at exterior of berm < 0.05 mRem/hr “unlimited occupancy”

The collimator and its shielding must meet or exceed the Radiological Requirements for ground water protection, surface water (collected by the Booster sump pumps), and human protection through limiting residual activation of the external surface of the collimators and the prompt dose at the exterior surface of the berm where personnel may be present.

Beam Parameters

This new compact 2SC collimator system will be installed and tested under the current 400 MeV injection operating conditions and therefore must satisfy the radiological requirements for expected scraping rates (defined below) at 400 MeV prior to PIP-II coming on-line. It is generally the goal of all collimation systems to provide a well shielded absorber to which large amplitude particles may be effectively captured to minimize their loss elsewhere, thus minimizing the activation of accelerator components outside the collimation region. The addition, of this new 2SC is anticipated to alleviate the some of the load on the existing system thus reducing the residual activation in the region of the existing collimation.

The exiting Booster collimation system made up of three absorbers with two located in the Long 6 straight section and one in the Long 7 straight section. These are used as single stage collimators with movable rectangular jaws capable of scraping in both planes. Figure 5-3 shows the residual activation measurements at 1 foot at the beginning of an access period in May 2019. Shielding design and amounts vary for different locations around the ring and small losses at higher energy produce larger



residual (c.f extraction losses). The standard Radiation Safety survey at the beginning of a shutdown cannot distinguish what lost particle energy was responsible for the measured residual. Typically, the collimation system only acts on beam at the injection energy and very early in the acceleration cycle. The insert table in the figure shows that the relative contribution to the total residual activation for the three major categories, injection, collimation, extraction, and the rest of the ring. We see that the beam loss in the region of the collimation system is responsible for about half of the activation around the ring. If we assume that all the activation in the extraction region comes from 8 GeV extraction and we remove this contribution, the distribution of the losses is shown in parenthesis (). This is still consistent with half of the residual activation is from the collimation region.

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Booster Residual Activation Measurements at 1 ft on May 11, 2019Average Booster throughput 2.35E17 protons/hr

Injection

Extraction

CollimationActivation Distribution

Collimation 48% (55%)Extraction 20% (0%)Injection 14% (23%

Rest of ring 18% (21%)

Figure 5-3. Residual Activation in the Booster tunnel in units of mrem/hr @ 1ft

Table 5-2 shows the beam parameters, operational assumptions, and collimator scraping and power handling capability for several operational scenarios. The three scenarios are shown in the three



columns are: 1) current 400 MeV operational mode, 2) an “upgraded” operational mode at 400 MeV, and 3) the PIP-II 800 MeV injection mode. We focus our attention on the last two columns which include the new 2SC collimator. The first column is for reference. The 2SC collimator system must meet the radiological requirements under the last two operational scenarios. The top section shows the Booster injection energy, injected intensity, beam energy/cycle, repetition rate, and power injected into the Booster under three configurations.

Table 5-2. Beam Scraping rates for applicable operational scenariosParameter Current "Upgrade" PIP-II Units

Beam energy 400 400 800 MeVprotons per hour 2.45E+17 2.80E+17 4.80E+17 pphprotons per sec 6.81E+13 7.78E+13 1.33E+14 ppsprotons per cycle 4.54E+12 5.19E+12 6.67E+12 ppBcreo rate 15 15 20 Hzbeam energy/cycle 290.4 331.9 853.3 Joulesbeam power 4.4 5.0 17.1 kW

Assumed eff @ inj energy 95 96 98 %lost particles/cycle 2.27E+11 2.07E+11 1.33E+11 pLpBclost particles/sec 3.40E+12 3.11E+12 2.67E+12 pLpsJoules lost per cycle 14.5 13.3 17.1 JoulesPower Lost 217.8 199.1 341.3 Watts

Fraction 0.50 0.50 0.50loss/cycle into all collimators 1.13E+11 1.04E+11 6.67E+10 pLpBcloss/sec into all collimators 1.70E+12 1.56E+12 1.33E+12 pLpsEnergy into all collimators 7.3 6.6 8.5 JoulesWatts into all collimators 108.9 99.6 170.7 WattsWatt distibuted around ring 108.9 99.6 170.7 Watts

Nbr Collimators 3 4 4Scraping rate 3.78E+10 2.59E+10 1.67E+10 pLpBc/collScraping rate for MARS 5.67E+11 3.89E+11 3.33E+11 pLps/collIncident beam energy/collimator 2.4 1.7 2.1 JoulesIncident beam power /collimator 36.3 24.9 42.7 Watts

Fraction of power loss going into collimators (from residusial activation)

Injected Beam Parameters

Acceleration Efficiency --> Beam Loss

Parameters/collimator (assume even distribution)

=

The next section discusses the Acceleration Efficiency and hence beam loss parameters (total beam loss, lost energy, and lost beam power for the assumed efficiency) for the entire Booster ring in the period from injection to shortly after the start of acceleration. Note that as the number of protons/sec increase under the last two scenarios the acceleration efficiency is increased. This assumption is based



upon improvements in Booster efficiency due to injection optimization, resonance correction and ultimately injection energy increase in PIP-II.

For purposes of modeling we look at the distribution of the residual activation around the ring, particularly the contribution in the collimation region, and use this to scale how much of the total loss ends up in the collimation system. It is understood that the measured residual activation levels around the ring do not necessarily directly reflect the particle loss rate at a specific location, due to differences in shielding, but we will use the 50% level of the acceleration in efficiency as a guide to scale the expected number of particles captured in the collimation regions.

The current collimation system has three single stage collimators and for this exercise it is assumed the current loss is divided equally among the three collimatord. From loss monitor data and the detailed residual activation measurements in the collimation region we know that currently the loss is not evenly distributed, but we will not address this detail at this time. With the addition of the new 2SC system, we assume this will make four collimation systems and the loss will be distributed evenly among all three. Again, this is for the purpose of sizing the shielding.

The last section gives the scraping rates and lost power for the collimator design to assure the shielding provides adequate shielding to satisfy the radiological requirements in Table 5-2.

5. Reference Documents

# Reference Document #

1 PIP-II Global Requirements Document (GRD) ED0001222

2 PIP-II Preliminary Design Report (PDR) PIP-II DocDB# 2261

3 V.V. Kapin et al, “Numerical Simulations of Collimation Efficiency for Beam Collimation System in the Fermilab Booster”, NAPAC-2016. -
