ORNL-SNS Diagnostic Group SNS Beam Loss Monitors and HARPs Machine Protection System FDR September 11,2001 Presented by Saeed Assadi

ORNL-SNS Diagnostic Group BLM System Requirements Numbers of installed units: DTL: 12  Type to be determined CCL: 24 SRF: 64 (Jan/01)  If all cryomodules present HEBT: 55 Ring: 87 RTBT: 43

ORNL-SNS Diagnostic Group SNS BLM System Status BLM system to be “Project-wide” Proposed design criteria established Preliminary detector locations established Preliminary ICD to Controls Group AFE circuit design: –Preliminary analysis done –PC prototype under test

ORNL-SNS Diagnostic Group SNS BLM SYSTEM DESIGN CRITERIA Upper end signal: – Maximum beam loss of 1 % at a single location –35-50 kHz signal BW –Beam interrupt via MPS based on integrated loss during pulse ( 10 μsec response) Lower end signal: –Set by 1 W/m requirement for maintenance –Must resolve 1% of 1 W/m but at BW of < 1 Hz –Warning only after extended period of loss (1 minute)

ORNL-SNS Diagnostic Group BLM AFE Configuration

ORNL-SNS Diagnostic Group BLM-- Specification: Fast Loss: 1)10 µsec Detect-to-Beam Inhibit time. 2) Programmable threshold, each detector, level changes/macro-pulse 3) Each detector maskable (eliminate bad channels, permit studies resulting in higher than normal losses) Single output line/analog crate Long-term: 1) Low level loss: "Soft" alarm through network or 2) Programmable threshold, each detector, 3) Each detector maskable (eliminate bad channels, permit studies resulting in higher than normal losses) Single output line/analog crate Local Data Storage: "Flight-Recorder Mode, 60 (1-second) records of "Detailed Losses" for each detector. Available for read-back on beam abort. In-Situ System check: On-line check of all detectors, connections and electronics by cycling HV Off/On.

ORNL-SNS Diagnostic Group BLM: Specification II Calibration: Each BLM detector and electronics channel shall have a measured and archived calibration. Packaging: No electronics in the tunnel. Minimum of 4 channels per analog module. Maximum of 32 channels per analog crate. Data acquisition uses VME environment Packaging: No electronics in the tunnel. Minimum of 4 channels per analog module. Maximum of 32 channels per analog crate. Data acquisition uses VME environment HV Cabling: Red RG-59 with SHV connectors (non-PTFE), (connected in daisy-chain). Signal Cabling: Non-tribo-electric cabling with BNC connectors (non-PTFE)

ORNL-SNS Diagnostic Group LINAC Dose Rate: ** Data is provided by Franz X Gallmeier.

ORNL-SNS Diagnostic Group LINAC Dose Rate (Simulated data) Distance along LINAC  Time 

ORNL-SNS Diagnostic Group Beam and Loss Display (Simulated data II)

ORNL-SNS Diagnostic Group SNS Linac Beam Size vs. Aperture Beam closest to pipe at start of DTL and end of CCL ** Slide from Sowmass 2001 talk by John Galambos

ORNL-SNS Diagnostic Group HARPS– Simulated profiles Certain wires could be monitored to predict the beam shape “stability”.

ORNL-SNS Diagnostic Group Max. Wire Temperature In The Injection Line (2 MW case) Data provided by C.J. Liaw

ORNL-SNS Diagnostic Group Maximum Wire Temperature In The Ring and RTBT Ring: Stationary or crawling wire: 1 MW case: 398 K 2 MW case: 450 K RTBT: Stationary or crawling wire: 1 MW case: 396 K 2 MW case: 460 K

ORNL-SNS Diagnostic Group SNS target harp lifetime Based on the observed lifetime of the HARPS used on LANCE, we predict the following lifetimes for the SNS Target HARP. Data provided by Mike Plum

ORNL-SNS Diagnostic Group Survivability of Wires: Carbon wires will survive (i.e.: wire temperature < 2000 K) in the entire injection line with a 6 Hz/50  s H - beam and can only be used in the higher energy region with the 6 Hz/ 1 ms and 60 Hz/1 ms H - beam. The wire temperatures in the ring and RTBT are low. Lifetime of the carbon wire is not an issue in these regions.

ORNL-SNS Diagnostic Group Conclusions: 1)SNS expects to maintain losses below 1Watt/meter over most of the Accelerator in order to allow hands-on maintenance. As such the BLM system will play a major roll in commissioning. 2)Important loss mechanisms include gas stripping, magnetic stripping and Halo generation from “mismatches”. We hope to use the BLM system to confirm the models and set the limits for the BLM-to-MPS trip levels. 3)Loss Monitor system will provide signals to the MSP system which are not modifiable by software (a layer of protection). 4)HARPS and specialized edge loss detection diagnostics are under studies but not included in the base-line systems yet.