A.2 SOW 10-15-2025.pdf

August 2021 Statement of Work 1

Statement of Work Title Absolute Beam Polarimetry at the Electron-Ion Collider

Sponsor [insert Sponsor’s Name] PIMS [insert # if applicable]

Lead PI & contact info

Duration of Performance

SOW Version

Frank Rathmann frathmann@bnl.gov +1 (631) 816 5933

3 years 1.0

Project Objective Aim of the project is the design of an absolute polarimeter system for the EIC.

The absolute polarimeter system builds upon two decades of experience from the RHIC accelerator and is comprised of the following key components:

• Polarized Atomic Hydrogen Gas Jet Target

• Scattering Chamber.

• Recoil Spectrometer

• Breit-Rabi Polarimeter (BRP)

Project Scope The scope of the project is the design and optimization of the different components of the polarimeter.

• Polarized Atomic Hydrogen Gas Jet Target providing the polarized atomic beam crossing the EIC proton beam perpendicularly.

• Investigation of source geometries and sextupole systems, nozzle configurations, etc., will be implemented by atomic beam simulation codes aimed at maximizing atomic flux and achieving optimal target density at the interaction point with the EIC proton beam.

• Scattering Chamber where the collisions between the target protons and the beam protons occur.

Recoil spectrometer detectors are mounted on both sides of the flanges.

• The ABS will be engineered for seamless installation and reliable operation as a target within the EIC environment, with careful consideration of vacuum requirements, radiation hardness, remote control capabilities, and minimization of any interference with the proton beam.

• A redesign of the magnetic holding field configuration is of particular importance, as due to the higher bunch repetition frequency at the EIC compared to RHIC, beam-induced depolarizing effects in the target need to be avoided.

• Options for magnetic holding field systems allowing guide field orientations along all three directions in space shall be explored. The potential of extracting all cartesian components of the beam polarization 𝑃𝑃�⃗ = (𝑃𝑃𝑥𝑥, 𝑃𝑃𝑦𝑦, 𝑃𝑃𝑧𝑧) shall be evaluated.

• Recoil Spectrometers will be utilizing silicon detectors to identify recoil protons and to measure their kinetic energy and time-of-flight (TOF) to select elastic scattering events.

• The recoil spectrometer functions by detecting recoil protons from proton-proton elastic scattering events. Recoil protons are identified using the non-relativistic relation between their kinetic energy (𝑇𝑇R) and TOF.

mailto:frathmann@bnl.gov

August 2021 Statement of Work 2

• The detectors select events within a specific TOF interval around the expected value for recoil protons of a given energy. The silicon detectors are positioned at specific azimuthal angles with respect to the magnetic holding field of the jet target. At RHIC each detector is 50 × 50 mm² in size with a 3.75 mm pitch, covering an azimuthal angle of 4°.

• The TOF of the recoil protons is measured relative to the bunch crossing time provided by the accelerator RF clock.

• The selected event yield is sorted by kinetic energy bins and further categorized by spin states and beam states (target, up-down, beam up-down) and individual detector segment.

This allows for the calculation of raw asymmetries and precise measurements of the analyzing power from which the beam polarization can be derived.

• Breit-Rabi Polarimeter (BRP) measuring the nuclear polarization of the atomic hydrogen of the

Atomic Jet.

Deliverables

Deliverable Description Due Date (in # of days or weeks after contract award) Do not put a specific date in here.

Preliminary Design Full design work up for review and approval

12 months ARO (after receipt of order)

Final Design Final design work up for review and approval

24 months ARO

Report Report on usage, maintenance, findings.

34 months ARO

August 2021 Statement of Work 3

Schedule

Task or Milestone Milestone

Duration (months)

Atomic Beam Source design: simulation calculations yes 18

Breit-Rabi polarimeter: simulation calculations yes 18

Scattering chamber design yes 36

Magnetic holding field design and simulations yes 36

Recoil spectrometer design and simulations yes 36

____________________________________ 10/15/2025_____________ Frank Rathmann Date Technical Representative