KIT – University of the State of Baden-Württemberg and National Research Center of the Helmholtz Association KIT Center Elementary Particle and Astroparticle Physics (KCETA) Institute for Nuclear Physics (IKP) www.kit.edu Commissioning of the KATRIN main spectrometer Nancy Wandkowsky for the KATRIN Collaboration NuMass 2013, Milano
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KIT – University of the State of Baden-Württemberg and
National Research Center of the Helmholtz Association
KIT Center Elementary Particle and Astroparticle Physics (KCETA)
Institute for Nuclear Physics (IKP)
www.kit.edu
Commissioning of the KATRIN main spectrometer
Nancy Wandkowsky for the KATRIN Collaboration
NuMass 2013, Milano
KIT – University of the State of Baden-Württemberg and
National Research Center of the Helmholtz Association
KIT Center Elementary Particle and Astroparticle Physics (KCETA)
Institute for Nuclear Physics (IKP)
www.kit.edu
Commissioning of the KATRIN main spectrometer
Nancy Wandkowsky for the KATRIN Collaboration
NuMass 2013, Milano
Introduction
Spectrometer commissioning status
Spectrometer background studies
Summary and Outlook
3 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
KATRIN experiment
Introduction
low endpoint β source
high count rate
high energy resolution
low background (<10-2 cps)
mν < 0.2 eV (90% CL)
key requirements:
4 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
KATRIN experiment
Introduction
low endpoint β source
high count rate
high energy resolution
low background (<10-2 cps)
mν < 0.2 eV (90% CL)
key requirements:
5
Spectrometer commissioning status
N. Wandkowsky - Commissioning of the KATRIN main spectrometer
adiabatic guidance of electrons by magnetic field
precise energy scan by retarding potential
low background: <10-2 cps
UHV in a huge spectrometer: O(10-11) mbar
Requirements for successful electron energy determination:
6
Spectrometer commissioning status
N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Major milestones achieved:
adiabatic guidance of electrons by magnetic field
precise energy scan by retarding potential
low background: <10-2 cps
UHV in a huge spectrometer: O(10-11) mbar
Requirements for successful electron energy determination:
air coil installation
7
Spectrometer commissioning status
N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Major milestones achieved:
wire electrode installation
adiabatic guidance of electrons by magnetic field
precise energy scan by retarding potential
low background: <10-2 cps
UHV in a huge spectrometer: O(10-11) mbar
Requirements for successful electron energy determination:
8
Spectrometer commissioning status
N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Major milestones achieved:
wire electrode installation
adiabatic guidance of electrons by magnetic field
precise energy scan by retarding potential
low background: <10-2 cps
UHV in a huge spectrometer: O(10-11) mbar
Requirements for successful electron energy determination:
air coil installation
9
Spectrometer commissioning status
N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Major milestones achieved:
Requirements for successful electron energy determination:
spectrometer bake-out
adiabatic guidance of electrons by magnetic field
precise energy scan by retarding potential
low background: <10-2 cps
UHV in a huge spectrometer: O(10-11) mbar
10 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer commissioning status
Air coil system
without any air coil system
distorted flux tube due to earth magnetic field
central field too weak (desired value: 3·10-4 T)
loss of signal electrons
B = 6 T B = 1·10-4 T
flux tube
11 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer commissioning status
Air coil system
with earth magnetic field compensation system (EMCS)
flux tube symmetric around spectrometer axis
central field too weak (desired value: 3·10-4 T)
loss of signal electrons
B = 6 T
EMCS
B = 1·10-4 T
12 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer commissioning status
Air coil system
with EMCS and low field correction system (LFCS)
central field at desired value: 3·10-4 T
full transmission
B = 6 T
EMCS LFCS
B = 3·10-4 T
13 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer commissioning status
Air coil system
with EMCS and low field correction system (LFCS)
central field at desired value: 3·10-4 T
full transmission & background suppression (factor 1000)
B = 6 T
e
EMCS LFCS
B = 3·10-4 T
14
Spectrometer commissioning status
N. Wandkowsky - Commissioning of the KATRIN main spectrometer
K. Valerius et al., Particle and Nuclear
Physics, Volume 64, Issue 2, April 2010
M. Prall, PHD thesis, Münster, 2011
250 modules, > 24000 wires
precision requirement 0.2 mm
compatible to UHV
Wire electrode
15
Spectrometer commissioning status
N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Wire electrode
electron energy analysis background suppression
U0
U1
U2
single layer: factor ~10
double layer: factor 100
smooth electric potential
maximal potential in center
16
Wire Electrode – completed (Jan. 2012)
Closing the vessel:
- back at vacuum in July 2012
- p ≈ 10-8 mbar
Th. Thümmler
N. Wandkowsky - Commissioning of the KATRIN main spectrometer
17 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer commissioning status
Spectrometer bake-out: motivation
minimize scattering on residual gas
UHV in a huge spectrometer (1240 m3): O(10-11) mbar
18 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer commissioning status
Spectrometer bake-out: motivation
minimize scattering on residual gas
UHV in a huge spectrometer (1240 m3): O(10-11) mbar
removal of water adsorbed on spectrometer surface
turbomolecular
pump
inner surface: 690 m²
19 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer commissioning status
Spectrometer bake-out: motivation
minimize scattering on residual gas
UHV in a huge spectrometer (1240 m3): O(10-11) mbar
removal of water adsorbed on spectrometer surface
activation of chemical pump (non-evaporable getter St707)
20 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer commissioning status
Spectrometer bake-out: procedure
slow heating/cooling (~1°C/h): expansion of vessel and electrode
temperature breakpoints: 200°C – water removal from vessel
300°C – activation of getter material
1,E-11
1,E-10
1,E-09
1,E-08
1,E-07
1,E-06
1,E-05
1,E-04
0
50
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pre
ssu
re i
n m
bar
tem
pera
ture
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°C
time in hours
Baking cycle (4. - 30.1.2013)
temperature
pressure
leak developed
pressure back to
10-11 mbar level
21 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer commissioning status
Spectrometer bake-out: procedure
0
50
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22 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer commissioning status
Spectrometer bake-out: procedure
fix point
expansion
insulator
movable point
23 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer commissioning status
Spectrometer bake-out: procedure
J. Wolf
0
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insulator
24 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
wire electrode installation
spectrometer bake-out
Spectrometer commissioning status
air coil installation
mm precision positioning
UHV compatibility
voltages successfully applied
no wires damaged
getter only partly activated
vacuum: 9·10-11 mbar
earth field compensated
full flexibility of field shaping
Major milestones achieved:
25 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
wire electrode installation
spectrometer bake-out
Spectrometer commissioning status
air coil installation
mm precision positioning
UHV compatibility
voltages successfully applied
no wires damaged
getter only partly activated
vacuum: 9·10-11 mbar
earth field compensated
full flexibility of field shaping
Major milestones achieved:
26 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer background studies
transmission of ß-electrons:
magnetic guiding &
electrostatic retardation
B [T]
e
e e
q [°]
trapping of electrons:
spectrometer acts as
a magnetic bottle,
long storage (h)
Commissioning measurements:
27 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer background studies
getter material contains radon progenitors
huge getter surface (porous material)
radon (noble gas) escapes into spectrometer volume
Stored electrons: source
28 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer background studies
Rn-219 half-life: 3.92 s
pump-out time: ~ 360 s
radon undergoes α-decay in the spectrometer volume
Eα = 6.8 MeV
recoiling Po and α absorbed at spectrometer wall
Stored electrons: source
29 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer background studies
radon undergoes α-decay in the spectrometer volume
electrons are created by: shake-off, internal conversion, Auger effect
implementation of model into simulation software KASSIOPEIA
Stored electrons: background model
30 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer background studies
F. Fränkle et al, Astropart. Phys. 35, 128 (2011), arXiv:1103.6238
F. Fränkle, PhD thesis at KIT (2010)
S. Mertens et al, Astropart. Phys. 41, 52 (2013) , arXiv:1204.6213
S. Mertens, PhD thesis at KIT (2012)
stored electrons scatter off residual gas → ionization → secondary electrons
high primary energies → thousands of secondary electrons
ring pattern on detector
Stored electrons: background model
pre-spectrometer
31 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer background studies
calculations for expected
rate of radon decays
@ main spectrometer
model for electron
emission in α-decay
Stored electrons: expectations for main spectrometer
32 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer background studies
calculations for expected
rate of radon decays
@ main spectrometer
model for electron
emission in α-decay
Stored electrons: expectations for main spectrometer
33 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer background studies
Monte Carlo results: 6·10-2 cps expected, non-poissonian distribution
sensitivity reduction by a factor ~ 2
S. Mertens et al, Astropart. Phys. 41, 52 (2013)
S. Mertens, PhD thesis at KIT (2012)
Stored electrons: influence on neutrino mass sensitivity
design value
34 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer background studies
electric dipole Electron Cyclotron Resonance
sensitivity reduction not acceptable
active background reduction methods needed
Stored electrons: reduction methods
magnetic pulse
35 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer background studies
electric dipole cryo-baffle
sensitivity reduction not acceptable
active and passive background reduction methods needed
Stored electrons: reduction methods
36 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer background studies
B
E
vdrift
vdrift
vdrift
vdrift
e-
𝑣 =𝑐
𝐵2 ∙ 𝐸 ⨯ 𝐵
100 V/m → radial drift of electron
electron drifted onto the spectrometer wall
Stored electrons: electric dipole
37 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer background studies
NEG-Pump
LN2 cooled
baffle
spectrometer
vessel
219Rn
Stored electrons: cryo-baffle
38 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer background studies
electric dipole Electron Cyclotron Resonance
Stored electrons: reduction methods
magnetic pulse cryo-baffle
39 N. Wandkowsky - Commissioning of the KATRIN main spectrometer
Spectrometer background studies
electric dipole Electron Cyclotron Resonance
Stored electrons: reduction methods
magnetic pulse cryo-baffle
40 N. Wandkowsky - Commissioning of the KATRIN experiment
Summary and Outlook
KATRIN: determination of mν <0.2 eV (90% CL)
Successful wire electrode and air coil installation
Successful bake-out of spectrometer
ToDo: attach detector system
Commissioning measurements for >1 year
Electron transmission
Background:
Cosmic muon induced
Radon induced
Passive & active background reduction methods
Prepare main spectrometer for tritium measurements