Big Gravitational Trap for neutron lifetime measurements A. Fomin Project leader: A. Serebrov PNPI, Gatchina, Russia Physics of fundamental Symmetries and Interactions - PSI2013 PSI, Switzerland 8-12 September 2013

Gravitrap  Big Gravitrap Increasing of “wide” trap volume is 5.3. Increasing of “narrow” trap volume is 18. Statistical accuracy 0.7 s → 0.2 s; Vacuum correction 0.4 s → 0.04 s; Measurement in two positions without disassembling; Improvement of loss factor ? 210-6 → 10-6 ? Expected accuracy: statistical ~ 0.2 s systematical < 0.1 s 878.5 ± 0.7stat ± 0.3sys s Phys. Lett. B 605, 72 (2005) Phys. Rev. C 78, 035505 (2008)

The method of neutron lifetime measurement with gravitationally trapped ultracold neutrons

Russian traditions Tsar Bell Tsar Cannon Tsar Gravitrap

Scheme of Big Gravitational Trap insert measurements without insert UCN trap UCN valve detector measurements with insert axis of trap and insert rotation UCN

Design of Big Gravitrap

Manufacturing of Big Gravitrap

Manufacturing of Big Gravitrap

MC simulation of neutron lifetime experiments MC simulation, data analysis: measured value nm initial value n0 nm  n0 =? MC code A.K. Fomin, PhD Thesis, PNPI, Gatchina, 2006 Gravitrap Phys. Lett. B 605, 72 (2005) Phys. Rev. C 78, 035505 (2008) MAMBO I JETP Lett. 90, 555 (2009) Phys. Rev. C 82, 035501 (2010) KI experiment JETP Lett. 92, 40 (2010) Big Gravitrap Technical Physics 11 (2013)

High precision Monte Carlo simulation PNPI computing clusters: 1. ITAD cluster - photo 2. PC Farm 6.41011 neutron histories 1.5 year of statistics accumulation

Time diagram of measurement cycle t, s , degree Etrap, neV filling 300 180 monitoring 500 15 60.1 holding 300; 2000 78.5 emptying 1 200 19 55.2 emptying 2 24 49.3 emptying 3 33 39.1 emptying 4

UCN spectrum for each of 4 emptyings

Extrapolation to neutron lifetime with insert without insert nm  n0, s without insert 0.05 ± 0.54 with insert –0.16 ± 0.32 joint –0.05 ± 0.10

Thermal screens Thermal screen “mushroom” near the bottom of the trap does not slow down emptying process.

Inserts of different height a b a c d e f b wrong spectrum  syst 0.05 s (with insert) No systematic because corresponding MC spectra will be used for  calculation.

Stiffening angle wrong spectrum  syst 0.01 s (without insert) No systematic because corresponding MC spectra will be used for  calculation.

Extrapolation to neutron lifetime with insert without insert nm  n0, s without insert 0.05 ± 0.54 with insert –0.16 ± 0.32 joint –0.05 ± 0.10

Plan of Big Gravitational Trap position at PF2 MAM at ILL EDM spectrometer Big Gravitational Trap UCN turbine

Conclusion Monte-Carlo model of Big Gravitrap is built. The systematic uncertainty connected with a method of calculation of effective frequency of UCN collisions in the trap is defined with value of 0.1 s. Manufacture of the setup is almost completed. Vacuum tests are done. Now cryogenic tests are planned.