The KATRIN experiment: calibration & monitoring

The KATRIN experiment: calibration & monitoring NPI Rez near Prague

content KATRIN overview < Am/Co measurements at Mainz < first Rb/Kr measurements at Mainz < multiple background events <

the KATRIN experiment > next generation tritium experiment > beta decay experiment > to measure neutrino mass > model independent way > compl. to double β decay & cosm. > sensitivity 0.2 ev (90%c.l.) (no signal) > discovery potential 0.35 ev (5 σ) > design report, 2005

calibration & monitoring interested in energy < voltage measured < matching each other calibration < no physical motivation < bias of 10 ev -> mass of 1e 6 ev < diff. of tritium & helium mass 1.7 ev < > stability of calibration monitoring > strong physical motivation > time change of bias of 0.03 ev > implies fictitious mass of 0.02 ev

Am/Co measurements at Mainz

Am/Co source > 241 Am gammas 26344.8 ± 0.2 ev > width better than 0.03 ev > half-life of 432 y > 1.11 GBq by Amersham > photoeffect on a Co foil > K-shell bind. eng. 7708.78 ± 0.02 ev > with respect to Fermi level > width 1.3 ev > el. kin. eng about 18636.0 ± 0.2 ev > chemical shifts 2.0 ev

Am/Co measurements history 3.5 3.0 2.5 count rate [Hz] 2.0 1.5 > autumn 2003, ESA 12 Rez/Prague > induced by X-rays 0.5 > MC by A. Spalek > spring 2004, Mainz > reassembled source part > autumn 2004, Mainz > understanding background > spring 2005, Mainz > final feasibility study ESA 12 measurement & MC sim. ^ 1.0 0.0 9000 9500 10000 10500 11000 energy [ev]

Mainz setup > source part reassembled > Am/Co source in the magnet B > pumped to about 2e 9 mbar > if baked up to 250 C > pumping speed 1500 l/s > a full electrode, two grids > air coils > Earth field compensation coils > tank pumped to 1e 10 mbar > segmented detector > 1.5 kev resolution

spectrometer performance > Rb/Kr K-32 line > energy of about 17824 ev > natural width of 2.8 ev > theoretical res. 1.5 ev @ 17.8 kev > el. inhomog. 0.5 V (rough) > HV ripple 0.8 V 22 20 18 16 14 12 10 8 6 4 2 0 17810 17815 17820 17825 17830 17835 17840 Energy [ev] > spec res. 1.5 ev > fitted position 17824.83 ± 0.03 ev > fitted width 3.16 ± 0.12 ev > chi^2/d.o.f. 0.94

the first scan 3340 3320 3300 3280 3260 3240 3220 3200 18560 18580 18600 18620 18640 18660 18680 Energy [ev] > vanishing effect > background of 3.2 khz

gamma background count rate [Hz] 9 8 7 6 5 4 3 2 1 > Am 26.3 & 59.6 kev gammas > Np X-rays > Am self-absorption > factor of 2.2 for 26.3 gammas > Am X-rays > all these emit electrons 0 0 10 20 30 40 50 60 70 energy [kev] the thinner Co foil the better < 0.1 µm on mylar foil, hard to sputter < 3.0 µm Co foil picked up < the thinnest, self-supported <

tilted source position > monel shielding 58 deg. > source tilted 65 deg. > 26.3 kev shielded completely > 59.6 kev suppressed significantly > transmission checked by 57 Co > lower by factor of 2 7 6 5 4 3 the tilted source holder ^ 57 Co K-14.4 line, the tilted way < 2 1 7260 7270 7280 7290 7300 7310 Energy [ev]

adiabatic way 2300 2200 2100 2000 1900 1800 1700 1600 16000 16500 17000 17500 18000 18500 19000 19500 20000 Energy [ev] > energy res. 4.2 ev @ 18.6 kev > 300 el./s > as expected

turning nonadiabatic 460 440 420 400 380 360 340 320 300 280 > energy res. 2.7 ev @ 18.6 kev > 3.6 T mag. A&B, 5.2 G an. plane > worse adiabacity > lower background > bck. component from the source > Np & Am X-rays > photoeffect on Co L-shells 260 240 16000 18000 20000 22000 24000 26000 28000 Energy [ev]

sputtering the foil > well defined surface > reproducibility > get rid of Co oxides > in favor of metal component > Ar ions of about 100 ev > about 16 nm of Co sputtered 335 330 reference sputtered 325 320 315 310 305 the setup during the sputtering ^ black before, and magenta after < 300 295 18600 18610 18620 18630 18640 18650 Energy [ev]

turning even more nonadiabatic 800 700 600 500 400 > fixing magnetic flux > 2.4 T mag. A&B, 0.56 T cm 2 > varying energy resolution > starting 3.9 ev (5.0 G) (black) > reaching the adiabatic edge > 2.4 ev (3.1 G) (magenta) > loosing the ability to guide el. > finishing 1.5 ev (1.9 G) > signal to background ration 300 200 100 17000 17500 18000 18500 19000 19500 Energy [ev]

turning even more nonadiabatic 700 600 500 400 300 200 100 > fixing energy resolution > (mag. field at the an. plane) > zooming the det. image > (varying detector field) > improving signal to bckg. ratio > paying the effect > getting space at the an. plane 0 17000 17500 18000 18500 19000 19500 Energy [ev]

nonadiabatic way 22 21 20 19 18 17 > energy res. 1.4 ev @ 18.6 kev > 2.4 T mag. A&B, 1.8 G an. plane > mag. flux 0.17 T cm 2 > effect of about 2 Hz > background of about 16 Hz > our best 16 18620 18622 18624 18626 18628 18630 18632 18634 18636 Energy [ev]

Am/Co conclusion good & stable source < to monitor & calibrate < > J. Bonn for sharing his experience, assistance & hospitality > E. Otten for valuable discussions, financial support > F. Glück for his code to calculate el. & mag. fields, and to track el. > B. Flatt for spec. introduction

first Rb/Kr measurements at Mainz, A. Kovalik INP Rez near Prague, ЛЯП ОИЯИ Дубна

Rb/Kr source > a convenient solid source > to monitor > June, 2005, Mainz > 29 kbq source (83Rb, 86 d) > evaporated at Rez/Prague > memo to be published

spectrometer setup > spectrometer magnets 45 A > mag. fields of 5.4 T > pumped to 5e-10 mbar > Rb/Kr in the magnet > pumped to 8e-9 mbar > no bake up > detector charged up 40 V > the inner segment only > moderate conditions

the first scan > Iair = 0 A > Ic = 60 A (1.7 T) full field > Ban. = 11.5 G, res. 3.8 ev > beam diameter of 43 cm > source diameter of 6.7 mm 15 16 14 12 10 8 14 13 6 12 11 10 4 17000 17200 17400 17600 17800 18000 Energy [ev] 9 8 7 6 17700 17720 17740 17760 17780 17800 17820 17840 Energy [ev] > a wide scan at the top > a zoom on the left

optimized position > keeping the setup constant > moving the source > 4.5 mm down, 1 mm left > signal to background ratio 80 70 90 80 70 60 50 40 30 20 60 50 40 10 16800 17000 17200 17400 17600 17800 18000 18200 18400 Energy [ev] 30 20 17700 17720 17740 17760 17780 17800 17820 17840 Energy [ev] > a wide scan at the top > a zoom on the left

improved resolution > Iair = -7.5 A > Ic = 35 A (1.0 T) > Ban. = 4.9 G, res. 1.6 ev > worse adiabaticity 40 40 35 30 25 20 15 35 10 30 25 20 15 10 5 17700 17720 17740 17760 17780 17800 17820 17840 Energy [ev] 5 16800 17000 17200 17400 17600 17800 18000 18200 18400 Energy [ev] > a wide scan at the top > a zoom on the left > background component coming from the source

optimized mapped area 60 50 Ic = 55 A Ic = 45 A Ic = 35 A Ic = 25 A 40 30 20 10 0 17000 17200 17400 17600 17800 18000 18200 18400 Energy [ev] > Iair = -7.5 A > Ic = 55, 45, 35, 25 A > Ban. 5.6, 5.3, 4.9, 4.6 G > res. 1.8, 1.7, 1.6, 1.5 ev

the K-32 line > Ic = 25 A, Iair = -7.5 A > analyz. plane field of 4.6 G > resolution of 1.5 ev > 29 % of the source mapped 20 18 22 20 18 16 14 12 10 8 6 4 2 16 14 12 0 17810 17815 17820 17825 17830 17835 17840 Energy [ev] 10 8 6 17810 17812 17814 17816 17818 17820 17822 17824 17826 Energy [ev] > the K-32 line at the top > low energy tail on the left

the K-32 line fitted > position about 17824 ev > width 2.8 ev > theoretical res. 1.5 ev > el. inhomog. 0.5 V (rough) > HV ripple 0.8 V 20 18 16 14 12 10 > spec. res. of 1.5 ev > position 17824.83 ± 0.03 ev > width 3.16 ± 0.12 ev > chi^2/d.o.f = 0.94 8 6 4 2 17820 17822 17824 17826 17828 Energy [ev] > spec. res. of 2.0 ev > position 17825.12 ± 0.03 ev > width 2.96 ± 0.12 ev > chi^2/d.o.f = 0.94 > 83mKr activity est. 1.9 kbq > gamma spec. 29 kbq > e.i. 6.6 % of 83mKr kept

L-9.4 lines > keeping the setup constant > resolution of 0.6 ev > detector eff. 3 times lower > both 83Rb & 83mKr decays 160 140 120 100 80 60 40 140 20 120 100 80 0 7000 7100 7200 7300 7400 7500 7600 7700 7800 7900 Energy [ev] 60 40 20 7450 7460 7470 7480 7490 7500 Energy [ev] > L-9.4 lines at the top > the L1-9.4 line on the left

L-32 lines > keeping the setup constant > resolution of 2.6 ev 70 60 50 40 30 40 35 30 25 20 15 20 10 0 30300 30350 30400 30450 30500 30550 Energy [ev] 10 5 0 30450 30455 30460 30465 30470 30475 30480 Energy [ev] > L-32 lines region at the top > the L3-32 line on the left

Rb/Kr conclusion & outlook all lines clearly observed < no disturbing backgrnd. < source quality superior < activity to be enhanced < Kr escape to be avoided < long term stability < > J. Bonn for assistance, ideas, experience shared, and financial support > F. Glück for his elmag. code > A. Spalek & D. Venos who prepared the source

multiple background events at Mainz, J. Bonn NPI Rez near Prague, Universität Mainz

experimental evidence 10 1 10 0 10-1 10-2 10-3 10-4 > B. Flatt: background, X-ray gun > N. Titov: background > the tritium runs & sweeping electrodes with HV > no evidence in the tritium data 10-5 0 50 100 150 200 250 300 350 400 Energy [kev] several electrons < with the retarded energy < at the same moment <

not an electronic effect 10 1 10 0 10-1 10-2 10-3 10-4 10-5 0 50 100 150 200 250 300 350 400 Energy [kev] > gammas not multiplied

a scope look

a scope look

independence of count rate > 1.11 GBq Am/Co vs. > pure spectrometer background > 25 kv vs. 18.6 kv (no reason) > the same behavior 10 1 10 0 10-1 10-2 Am/Co induced, U 0 = 25.0 kv pure background, U 0 = 18.2 kv 10-3 10 0 10-1 Am/Co induced, U 0 = 25.0 kv pure background, U 0 = 18.2 kv 10-4 10-5 0 20 40 60 80 100 120 140 160 180 200 Energy [kev] 10-2 10-3 10-4 the first segment data on the top ^ the third segment data on the left < 10-5 0 50 100 150 200 250 300 350 400 450 Energy [kev]

mirrors and traps > spectrometer a magnetic trap > analyzing plane & magnets > canceled by I_B = 0 A & > strong counter-field I_air = 10 A. > electrodes directly mapped 10-1 10-2 10-3 I B = 50 A I B = 0 A 10-4 10-1 I B = 50 A I B = 0 A 10-2 10-5 0 20 40 60 80 100 120 140 160 180 200 Energy [kev] 10-3 10-4 the first segment data on the top ^ the third segment data on the left < 10-5 0 50 100 150 200 250 300 350 400 450 Energy [kev]

shaping time > 3 µs vs. 1 µs > too slow to separate the events 10 2 10 1 10 0 3 µs 1 µs 10-1 10-2 10-3 10 1 10 0 3 µs 1 µs 10-4 10-5 0 50 100 150 200 250 300 350 400 Energy [kev] 10-1 10-2 10-3 10-4 the first segment data on the top ^ the third segment data on the left < 10-5 0 50 100 150 200 250 300 350 400 450 Energy [kev]

energy resolution 101 100 10-1 > 1.5 G, 1.3 G, and 1.1 G > 1.2 ev, 1.0 ev, 0.9 ev @ 18.6 kev > diam. of 47, 50, 55 cm first seg. > diam. of 80, 87, 94 cm third seg. > full electrode of 100 cm in diam. > grids with diam. of 89, 80 cm Ban = 1.5 G Ban = 1.3 G Ban = 1.1 G 10-2 10-3 10-4 101 Ban = 1.5 G Ban = 1.3 G Ban = 1.1 G -5 10 100 0 50 100 150 200 250 Energy [kev] 300 350 400 10-1 -2 10 the first segment data on the top ^ the third segment data on the left < 10-3 10-4 -5 10 0 50 100 150 200 250 Energy [kev] 300 350 400 450

beam diameter > diam. of 47 (80) cm 1 st (3 rd ) seg. > 1.2 ev (1.5 G) @ 0.26 T cm 2 > 2.4 ev (3.0 G) @ 0.51 T cm 2 > 2.0 ev @ 0.51 T cm 2, 47 -> 50 cm > neither resolution nor beam diam. > adiabacity driven 10 1 10 0 10-1 10-2 10-3 Φ = 0.26 T.cm 2, d an = 47 cm, res. 1.2 ev 18.6 kev Φ = 0.51 T.cm 2, d an = 47 cm, res. 2.4 ev 18.6 kev Φ = 0.51 T.cm 2, d an = 50 cm, res. 2.0 ev 18.6 kev 10 1 10 0 Φ = 0.26 T.cm 2, d an = 47 cm, res. 1.2 ev 18.6 kev Φ = 0.51 T.cm 2, d an = 47 cm, res. 2.4 ev 18.6 kev Φ = 0.51 T.cm 2, d an = 50 cm, res. 2.0 ev 18.6 kev 10-4 10-5 0 20 40 60 80 100 120 140 Energy [kev] 10-1 10-2 10-3 10-4 the first segment data on the top ^ the third segment data on the left < 10-5 0 20 40 60 80 100 120 140 Energy [kev]

adiabacity > 2.6 G, 3.8 G, 4.9 G, and 6.1 G > 1.9, 2.8, 3.6, 4.5 ev @ 18.6 kev > narrowing the beam flux > suppressing the effect > Am/Co spec. to be subtracted 10 2 10 1 10 0 10-1 10-2 res. 1.9 ev 18.6 kev, d an = 50 cm res. 2.8 ev 18.6 kev, d an = 41 cm res. 3.6 ev 18.6 kev, d an = 36 cm res. 4.5 ev 18.6 kev, d an = 33 cm 10-3 10 1 10 0 10-4 res. 1.9 ev 18.6 kev, d an = 86 cm res. 2.8 ev 18.6 kev, d an = 72 cm res. 3.6 ev 18.6 kev, d an = 63 cm res. 4.5 ev 18.6 kev, d an = 57 cm 10-5 0 20 40 60 80 100 120 140 Energy [kev] 10-1 10-2 10-3 10-4 the first segment data on the top ^ the third segment data on the left < 10-5 0 20 40 60 80 100 120 140 Energy [kev]

screening voltage > 1.8 G, 1.3 ev @ 18.6 kev > +5 V, +10 V, +15 V screening > both the intermed. & dipole el. > can cure the effect 10 2 10 1 10 0 10-1 10-2 U = +0 V U = +5 V U = +10 V U = +15 V 10-3 10 1 10 0 10-4 U = +0 V U = +5 V U = +10 V U = +15 V 10-5 0 20 40 60 80 100 120 140 Energy [kev] 10-1 10-2 10-3 10-4 the first segment data on the top ^ the third segment data on the left < 10-5 0 20 40 60 80 100 120 140 Energy [kev]

true secondary electrons 0.06 0.05 0.04 Probability 0.03 0.02 0.01 0 0 50 100 150 200 Energy [ev] > secondary electron emission > elastical reflection > redifussion > true secondary electrons phenomenological prob. model < by M.A. Furman & M.T.F. Pivi < LBNL-52807 (2003) <

probability of the process 0.4 0.35 0 rad π/8 rad π/4 rad 3π/8 rad 0.3 0.25 Probability 0.2 0.15 0.1 0.35 0.3 0.25 E 0 = 10 ev E 0 = 50 ev E 0 = 70 ev E 0 = 100 ev E 0 = 200 ev 0.05 0 0 50 100 150 200 Incident energy [ev] Probability 0.2 0.15 0.1 incident energy dependence - top ^ incident angle dependence - left < 0.05 0 0 π/8 π/4 Incident angle [rad] 3π/8 π/2

yield per incident electron 1.6 1.4 0 rad π/8 rad π/4 rad 3π/8 rad True secondary electrons yield 1.2 1 0.8 0.6 0.4 True secondary electrons yield 1.4 1.2 1 0.8 0.6 0.4 E 0 = 10 ev E 0 = 50 ev E 0 = 70 ev E 0 = 100 ev E 0 = 200 ev 0.2 0 0 50 100 150 200 Incident energy [ev] incident energy dependence - top ^ incident angle dependence - left < 0.2 0 0 π/8 π/4 Incident angle [rad] 3π/8 π/2

yield per penetrated electron 30 25 0 rad π/8 rad π/4 rad 3π/8 rad True secondary electrons yield 20 15 10 True secondary electrons yield 45 40 35 30 25 20 15 10 E 0 = 10 ev E 0 = 50 ev E 0 = 70 ev E 0 = 100 ev E 0 = 200 ev 5 0 0 50 100 150 200 Incident energy [ev] incident energy dependence - top ^ incident angle dependence - left < 5 0 0 π/8 π/4 Incident angle [rad] 3π/8 π/2

a simulation mockup > few tens of electrons produced > to be guided to the detector > have to be bound on a field-line > a nonadiabatic process > driven by plasmons (problably) > as for the reflected ones > they may hit the electrode again > to leave & bind on a field-line > they hit the detector ~1 µs later > repeatedly some reflected by the mag. field< not many of them < energy < resolution accepted < energy > resolution high prob. <

multiple events conclusion & outlook multiple background events < driven by lack of adiabacity < true secondary el. suggested < simulation offered < unknown nonadiabatic process < a threshold energy study? contribution to tritium background? > F. Glück for his code to calculate el. & mag. fields, and to track el. > E. Otten for valuable discussions

acknowledgment O. Dragoun < A. Kovalik, ЛЯП ОИЯИ Дубна < M. Rysavy, A. Spalek, D. Venos < J. Bonn, E. Otten, Universität Mainz < F. Glück, FZK Karlsruhe < B. Flatt, Universität Mainz <