Beam on Target Diagnostics Beam on Target Meeting 2013 March Tom Shea

Goals Support commissioning/studies of beam expansion section and target/dumps Support rapid production setup (maximize neutron production) Assure operations within approved envelope Minimize beam-induced damage to target and dump system components Support neutronics studies Record accelerator performance

(Old) Requirements Measurement accuracy based on the preliminary Accelerator to Target Interface table Requirements are similar for beam measurement at Target, Proton Beam Window, and Dump Also: interface to MPS, buffering of data, event-driven data acquisition, beam accounting Normal Condition Off-normalRatio Allocation for instrumentation error Beam power within 160 mm by 60 mm >90 % > 50% power outside spot 40% (referred to full power) 20% Peak time- average beam current density ≤0.47 A/m^ 2 >0.47 and ≤0.64A/m^ 2 36% (referred to nominal) 20% Peak single pulse density ≤2.09 x 10^17 protons/m^ 2 >2.87 x 10^17 prot/m^ 2 37% (referred to nominal) 20% Tolerance on beam centroid relative to global coordinates ±6 mm> +/- 6 mm Horizontal: 4% of beam size Vertical: 10% of beam size +/- 3 mm or 10% of vertical beam size Preliminary interface: McManamy Old estimates – will be revised

Accelerator to Target Line 25 mm 200 mm Simulation with 500,000 particles Simulation data: Aarhus

Tom Shea, ESS, Beam Shaping Workshop, Aarhus, Beam-on-Target Based on preliminary interface definition: Measure beam density with 20% accuracy, centroid with 3 mm accuracy Upstream wire scanners to measure emittance (not shown here) BCM shown above: – Used to normalize beam density measurements, also used by neutron instruments – Beam accounting (power on target, total energy delivered, etc) Redundant measurements at proton beam window and target: – Halo: Halo monitoring via thermocouple assemblies – Img: Imaging (luminescent coatings on Proton Beam Window and Target) – NPM: Non-Invasive Profile monitor (He gas luminescence) – Grid: SEM in vacuum and ionization in Helium He at ~1 atmvacuum

Space is Allocated in Target Monolith Target shaft Target diagnostics (no details yet) Target wheel Beam Instrumentation Plug Optics (upstream, downstream, H and V) H and V grid halo PBW: Coating (<100 C) H and V grid halo PBW plug He-valve plug Access to water cooled shielding blocks (if necessary) Coating on target (<200 C) 4.4 meters Optical and signal path Drawing: Jülich

Images vs. Wavelength ESS imaging: Use spectral filtering to separate coating emission from Helium gas luminescence Data from SNS

Tom Shea, ESS, Beam Shaping Workshop, Aarhus, Proton Beam Window Panpipe proton beam window helium cooled Drawing: Jülich Locate halo thermocouples on window frame Integrate wire grid into assembly Develop coating for window

Proton Beam Window halo thermocouples Thermocouples for Halo monitoring & Beam Centering SNS example

Multi-wire Grid: Ionization monitor in Helium 10 6 protons in the simulation, flat beam 1 cm * 1 cm 2.5 GeV, no energy spread no divergence Proton beam widow, 1 mm Al Detector, 3 cathode separate by 1 cm thickness = 0.1 mm Al target 50 cm390 cm Helium atmosphere after the window Profile measurement with multi wire proportional chamber used in ionization mode Simulation: Benjamin

At Grid Location Protons neutron γ Electron neutron γ π + π - assuming a cell size of 1mm(trans) * 1 cm (long.) with full power the current on the wire is 3.5 mA. the ratio between the proton and the particle in the shower ( mainly pions and electrons) is around 10^-4, the particles have a high energy and we can assume that the signal given by the shower has the same ratio as the proton. Full power allowed

Tom Shea, ESS, Beam Shaping Workshop, Aarhus, Raw SEM Signals at SNS Wire position (mm) Amplitude (a.u.) SEM signals: How fast can we acquire with reasonable S/N?

Tom Shea, ESS, Beam Shaping Workshop, Aarhus, Slow Scan observed by SNS Imaging System

Tom Shea, ESS, Beam Shaping Workshop, Aarhus, Effect of Beam Position on Neutron Production – pencil beam Iverson, Shea Goal: support neutronics studies

Machine protection and interlocks Risk assessment – Worst case: Analyze impact of static beamlet. Can we survive single pulse? Time to mitigate? – Analyze other failure modes (with Scandpower – Annika leads?) Redundant MPS inputs – Direct detection of power converter/kicker problems – Measurement of beam position vs. time. Position electrodes at proton beam window and upstream. – Profile measurements (imaging and wire grid, possibly He luminescence) – Ionization monitor: measure position even in case of saturation? – Loss monitors, halo montors? – Target instrumentation??

Conclusion and Next Steps Requirements have been developed based on preliminary Accelerator to Target Interface. These can be refined as target, beam window, and, dump designs proceed; and as rastering option is considered. Techniques identified for all required measurements and preliminary locations identified for components Technical challenges of baseline system will be addressed with focused R&D program – Luminescent coating for window low-mass window and higher temperature target – Development of broadband, radiation-tolerant optical systems – Development of ionization monitor As we refine beam to target strategy and evaluate rastering, what additional activities are required in instrumentation and interlocks?