n _TOF facility status (13/12/2010 – 06/10/2011)

1. n_TOF facility status(13/12/2010 – 06/10/2011) E. Berthoumieux on behalf the n_TOF collaboration

2. Outlines • Proton status • Neutron beam line status • Status of the 2010 gas release problem • Status of the moderator & cooling circuit • Remaining RP issues • Foreseen / possible facility upgrade • RP related • Access related • In the neutron beam line • DAQ related

3. Proton status • Reminder: proton is read by a new transformer since beginning of this year to solve the saturation problem • We are about to reach our planned intensity for 2011 • n_TOF Ph2 target received more beam than old one (>3.4 1019 p)

4. Neutron beam line status • Reminder: First collimator not (and can not be) aligned. • Small leakage at the filter station level (probably with the C filter) • Several general electricity cuts occurred this year causing sometimes difficulties to restart the pumping, the magnet or the DAQ • Sweeping magnet switched off due to a “current balance” alarm. No real causes found by the expert. • EM & grounding problems in the WSTA. • Fences are being replaced to avoid intrusion in the WSTA

5. n_TOF inside ISR-8 Degassing duct (~60 m) n_TOF ventilation ~30 m2 Ventilation duct n_TOF cooling station ~70 m2

6. 2010 gas released problem (EDMS 1147942) • Maximum personnel exposure in 2010 due to the n_TOF cooling station External photon dose rate meas. • Estimation of relative contribution of the skin and inhalation dose • n_TOF operating conditions (beam and degassing) • Occupation factor

7. Modifications on moderator circuit (reminder) • Cationic to mixed bed (previously saturated in enriched boron thanks to the bench test) resins. • No raise in conductivity seen since the filling of the circuit • Moderator circuit was not designed to switch twice a year from demineralized to borated water • New expansion vessel to fill and check the water level in the moderator circuit • New valves and pipes to empty the circuit. • Filling/emptying only require now valves manipulations. • Circuit was filled with enriched boric acid (not the same as last year!!!) the 1st of march and boron (~1 kg) was added in the “pot à bore” the 8th of march

8. Moderator station status • Moderator circuit working at the saturation limit (filled with water containing 41.8 g/l of boric acid) • Some difficulties to have a stable regime in the borated water circulation at start-up. • Colder chilling water (7±2 ºC) and higher chilling water flow inside the “pot à bore” to ensure that it remains the coolest point of the moderator circuit • Conductivity very stable up to now (~57 µS) • A water leakage (~1.5 l loss in 6 months) was found at the TT9 sensor position. • Fixed but still under surveillance

9. Cooling station status • Shielding has been reinforced during 2010 shutdown • Still not sufficient (see RP issues later) • Leakage of the degassing circuit solved • This circuit is now a radioactive source! • Problem with the oxygen content measurement • Value read by the station is wrong: shift of >0.04 mg/l compared to the value directly read on the apparatus. • Threshold have been modified to take care of this shift. • Action to be done during next shutdown to solve the problem

10. Remaining RP issues (from J. Vollaire) • Dose rate in the vicinity of the cooling station can be still above the CERN limit for a non exposed area Blocks added here • Blocks added (31/08/2011) to overcome this issue • 2 workplaces • Center • Right Detector at the center

11. Remaining RP issues (from J. Vollaire) • Results are normalized to alarm A level on PMITOF03 (= 6 mSv/h alarm B = 7 mSv/h) • Effect seems visible but is not sufficient to declassify the area with the current nominal intensity and alarm levels

12. Summary of known problems in ISR8 Duct is a radioactive source Dose > 2.5 µSv/h Noise problem (not an n_TOF issue) Dose > 0.5 µSv/h

13. RP related possible facility upgrade (ISR8) • Remaining dose at workplace area assigned to skyshine effect. • Dose in front of cooling station due to combination of skyshine effect and degassing duct. Foreseen/possible upgrades • Permanent RP monitoring at workplace area (RP action already started) • Send degassing duct directly to primary area • The initial idea to just replace existing duct has been abandoned • Roof (total or partial) over the station

14. Access system in primary area willberevised(EDMS 1145465, 1145476 & 990214) • PS complex access system will be completely revised during the long shutdown • GS/ASE mandate will be focused on access only • Ventilation of primary area will be part of the access system • Cooling station will no longer be interlocked with beam!!!

15. upgrades in the neutron beam line • Filter station • Solve the leakage problem • Add/replace some filters? • 1st collimator alignment? • Magnet control (~30 years old, lack of spares pieces) • Grounding improvement in WSTA • EM decoupling of the beam pipe nearby the WSTA? • Improve alignment in WSTA?

16. Current DAQ limitation Hardware • 8 bits digitizers (sometimes difficult to have low threshold and wide energy range) • Data transfer rate (<1 Gb/s) • Limited number of channels/stream • Not possible to go down to thermal (TAC@250 or 500 MS/s) Software • Still in 32 bits OS (RAM and filesize limitation) • GUI still based on Qt 2 version (current Qt 4)

17. DAQ possible upgrade • 8 channels, 12 bit, 1 GS/s, 64 MS/channel digitizer are now (next month) available on the market • Use of AXIe standard: PCIe X4 (2 GB/s) backplane connection • Cost/channel similar to DC282 (with memory extension)

18. DAQ software improvement • 32 to 64 bits OS migration • Mandatory if one want to use more memory/channel (to go down to thermal energies) • 8 bits to 16 bits raw data format • DC282 are already 10 bits capable (limited interest because number of effective bits is 6 as for DC270) • Go to a (lossless) compressed data format • Current DAQ peak capabilities (Am/Be): 200 MB/s (17 TB/day) • TAC down to thermal at 16 bits is up to 12 times more data! • Migration to up to date libraries (Qt4, socket, …) • Improved zero suppression? • Improved Event display • … • Raw format modification -> DST rewriting Manpower needed to implement these changes (and also to ensure the DAQ maintenance)