1. NMLTA Protection System Update -Loss Monitors- Arden Warner September 2 nd, 2009

2. 2 Loss Monitor Types The NMLTA MPS will rely heavily on Loss monitoring for fast protection. Considering three loss monitor types based on the following locations  Beam line (away from dumps) Type 1  Inside cryomodules (dark current monitoring) Type 2  Near dumps (high radiation areas) Type 3 Type 1 : Plastic scintillator type  PMTs with plastic scintillators  EJ-208 (1 ns rise time)  Radiation hard

3. 3 EJ-208 Plastic Scintillator Properties

4. 4 Fast Loss Monitor Specifications

5. 5

6. 6 Cryogenic Ionization chamber Type 2 : Cryogenic beam loss monitors can be operate from inside the cryomodules from 5k to 350k. Design Properties:  Stainless steel vessel, 120 cm3 filled with He-gas.  He-gas pressure of 1 bar (0.98 atm)  Sensitivity 1.9 pA/(Rad/hr)  Readout via current-to-frequency converter (1.9Hz/(Rad/hr)  Range: up to 30 kRad/hr  Pulses can be sent through long cables

7. 7 Cryogenic Ionization chamber 5k – 350K It is a helium-filled ionization chamber. It's current is proportional to the dose rate. ● The signal current is processed by a current to frequency converter to achieve a wide dynamic range and quick response dose rate excursions. ● All materials used are know to be radiation hard and suitable for operation at 5K. ● The electronics is self-contained and requires no computer to operate.

8. The chamber housing is held at negative potential and negative charge is collected on the center electrode. The HV is -95 V and is kept well below the minimum breakdown voltage of 156V in Helium. Cryogenic Loss Monitor operation The electronics uses a recycling integrator as a current to frequency converter with a wide dynamic range. The charge per pulse is 1 pC. The recycling integrator consist of a charge integrating amplifier with a 0.50 pF capacitance followed by a discriminator which senses when the capacitor is fully charged. The FPGA generates a fixed-width (400 µs) discharge pulse with an amplitude of 3.3V. It connects to the amplifier input via a 13 MΩ resistor, creating a 254 nA discharge current

9. 9 Secondary Emission Monitors Type 3: Near the NML dumps the radiation levels will be high. Secondary Emission Monitors are useful for monitoring electron beams at high dose rates since it is a vacuum device and free of the saturation problem encountered by ionization chambers. In the SEM, the current associated with secondary electrons ejected from a thin foil is collected and used to monitor the electron beam. Additional Properties:  High Linearity  Low sensitivity  Fast response Consider using SEMs with Ti electrodes because of secondary emission yield stability.

10. 10 Beam Loss Monitor System Requirements The majority of the BLM will be plastic scintillators with PMTs. An unscientific count based on the length of the machine and layout gives a total of ~ 45 - 50 loss monitor (1pair/3 m) for redundancy. Loss monitors have to be integrated into a VME based loss monitor system with the capability to:  Generate alarms based on user defined thresholds  Generate several alarm types based on location  Monitor PMT high voltage  Produce test pulse signal  Communicate with server (ACNET)  Time stamp and Archive Several modules will therefore be employed to analyze the beam loss, derive an alarm condition and provide an alarm message.

11. Example from DESY

12. 12 Cryogenic BLM Scintillator BLM SEM BLM

13. stop Gate BLOCK Block Laser GUN RF Machine Protection System Machine Infrastructure Magnet Status Machine Status Power Supplies Beam Mode Low charge, Full beam RF Status Cryogenics Vacuum OTR Screens In/out Slower Signals (< 200ms) PLC based Status BLM Beam Loss Monitors BLM Beam Loss Monitors Fast RF Signals Sparks, Quench, …. Fast RF Signals Sparks, Quench, …. Transmission Charge, position Transmission Charge, position Fast Signals FPGA Fast System Reaction time: Within the Bunch-train Reaction time: Pulse to Pulse Fast Events Fast Kicker Slot ‘0 ‘controller

14. FPGA Operation mode Beam mode Alarm reset Gun Permit Dark Kicker Permit RF Permit Long Bunch Permit Short Bunch Permit Single Bunch Permit Alarms PERMIT SYSTEM latched Mask Mapping reset alarms modes Mask Mapping reset alarms modes latched Sum Box Permit FPGA