Transcript Commissioning of the Radiofrequency quadrupole cooler

Commissioning of the
Radio Frequency Quadropole Buncher Cooler
TRIµP – Trapped Radioactive Isotopes:
µ-laboratories for fundamental Physics
U Dammalapati, S. De, P G Dendooven, O Dermois L. Huisman, K Jungmann, A.J. Mol, G Onderwater, A
Rogachevskiy, M Sohani, E Traykov, L Willmann and H W Wilschut
Lorenz Willmann
SMI-06, Groningen 27/28.3.2006
TRImP project and facility
Magnetic
Separator
Ion
Catcher
RFQ
Cooler
Atomic Physics
Production
Target
Nuclear Physics
AGOR
cyclotron
Wedge Q
MeV
D
Particle Physics
Q Q
Q
D
D
Q
Q
D
keV
Production
target
Q
Q
eV
Thermo Ionizer:
Thermo-ioniser
meV
Talk by M. Sohani
MOT
Beyond the
Standard Model
TeV Physics
Magnetic separator
RFQ cooler/buncher
neV
AGOR cyclotron
MOT
MOT
Low energy beam line
Trapped Radioactive Isotopes: micro-laboratories for Fundamental Physics
Experimental Program of TRImP group
Investigating discrete symmetry violations C, P, and T.
• Origin of Parity Violation
in Weak Interactions
•
 details of b-decays
Na, Ne isotopes
•
Dominance of Matter over Antimatter
CP - Violation
Time Reversal Symmetry
Parity Violation
 permanent electric dipole moments
Ra isotopes
Why do we need neutral atom
traps?
The role of atom trapping
• long storage times
• isotope (isomer) selective
• spin manipulation
• point source, no substrate
• recoil ion momentum spectrometry
• state preparation (for APNC,edm…)
• “low” EM fields (otherwise ion traps)
• Ideal environment
for precision experiments
Magnetic
Separator
Ion
Catcher
RFQ
Cooler
Atomic Physics
Production
Target
Nuclear Physics
AGOR
cyclotron
TRImP project and facility
Magnetic separator
Wedge Q
MeV
D
Q Q
Particle Physics
D
D
Q
Q
D
keV
Production
target
Q
Q
eV
meV
AGOR cyclotron
MOT
Beyond the
Standard Model
TeV Physics
Q
MOT
neV
MOT
Low energy beam line
Trapped Radioactive Isotopes: micro-laboratories for Fundamental Physics
TRImP RFQ cooler/buncher concept
• RF capacitive coupling
• DC drag resistor chain
2 x 330 mm
U+VcosWt
-(U+VcosWt)
• Standard vacuum parts (NW160)
• UHV compatible design and materials
• RF: 05-1.5MHz, 200Vpp,
Buffer gas pressure (He):
~10-1
10eV
~10-3
mbar
RFQ ion cooler
thermal
Trap position
mbar
RFQ ion buncher
Switching on end electrodes
RFQ System/Drift Tube
Pulsed
extraction
tube
RFQ
buncher
RFQ
cooler
Ion Pulses to
experiments
pHe ~ 10-6 mbar
Beam
from TI
pHe ~ 10-3 mbar
pHe ~ 10-1 mbar
Background pressure 10-8 mbar
RFQ Rods:
• Many UHV resistors
• segments individually coupled
• flexible axial potential design
• few RF connections
Drift tube Accelerator:
• ideal for pulsed setup
• no HV platform
Transmission efficiencies with He buffer gas
80
23Na+
ions
@ 10 eV, 15 eV
70
60
pA
pA
U(acc) = 10 V,
V 15 V
p(1):
p(1) =from
3.5*10
10-6-2 to
mbar
10-1 mbar
U(4): from 0 V to +36 V
(EL2),
EL3 and
(EL3)
(10)and
connected
(10)
to
pA-meter
connected to pA-meter
(11) at same potential as (1)
pA
50
40
30
20
10
0
-10
0
-20
EL1
EL2
EL3
MCP
Ion
Source
(1)
p(1)
(8)
(11)
(7) (9) (10)
p(2)
(3) (5)
(4)
Low Energy
beam line
 (RFQ1) = I(EL3+10)/I(load) =
= I(10)
50÷70%
Both I(EL2) and
increase with
increase of difference between U(3,5) and U(4)
(DU  14 V)  (RFQ2) = I(10)/I(EL3+10) =
= 50÷80%
22
10
20
9
18
8
I(EL2) RF off
16
7
12
10
8
6
I [pA]
14
6
5
I(EL3)
4
3
I(EL2)
2
4
2
Drift tube
1
0
I(10)
0
1.0E-05
0
5
10
1.0E-04
15
20
25
U(3,5) - U(4) [V]
1.0E-03
I(EL3)
I(10)
30
35
40
1.0E-02
Acceleration-deceleration
 (RFQ1+RFQ2) = I(10)/I(load) =
essential
for transmission
= 25÷40%
between RFQ1 and RFQ2!
I(load) = max.(I(EL2)+I(EL3)+I(10))
1.0E-01
Simple Diagostic Tool: MCP with phosphor screen
• Positional resolution, transverse emittance
• Counting mode for low rate
-2
119 V pp
2
2
y [mm]
y [mm]
2
-2
2
-2
-2
x [mm]
x [mm]
120 V pp
Filling of trap with different loading rates
Space charge limited
Heater Current
On ion source
Storage times of RFQ buncher
Storage time limitations:
- Space charge effect
- Impurities in the gas
3.5.10-4 mbar He gas (~10-8 mbar background)
Na+ ions remaining in trap [%] .
100
10
1
0
5
10
Storage time [s]
without baking of system and standard gas purity (Helium 5.0)
15
Direct detection of ion pulse on readout electrode
Signal [V]
Charge integrating amplifier
• rise time
40 nsec
• integration time
20 msec
• sensitivity
1 mV/1500 ions
• noise
3 mV
Storage time
100 msec
10 msec
1 msec
Extraction pulse
Drift tube pulse
Time [ms]
Data averaged
over 128
extraction cycles
TRImP RFQ cooler buncher system
• Storage time several seconds achieved
-> purity of buffer gas
expected 21Na production rate fills trap in 1s
• Drift tube accelerator -> no high voltage platform
• Good transmission > 70% of RFQ
• Vacuum conditions good to couple to Magneto-optical
Trap
More results in the forthcoming thesis of Emil Traykov
Coupling of RFQ and Low Energy beamline to MOT
Trapping while operating RFQ achieved last Friday
-> good differential pumping