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Argonne National LaboratoryOperated by The University of Chicagofor the U.S. Department of Energy Office of Science
U.S. Department of Energy
Applications of psec TOF in proton and heavy-ion accelerators
Peter OstroumovPico-Sec Timing Hardware Workshop
November 18, 2005
2PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Outline
● TOF measurements in accelerators RareIsotopeAcceleratorFacility Acceleratedbunchedbeamvelocity(energy)measurements
basedoninducedrfsignals Bunchtimeprofilemeasurementswithresolution~10
picosecondsbasedonstreakcamera
● Improvement of time resolution of the existing BLD
● Bunch time structure measurements using X-rays Highresolutionisobtainedbyusingstreakcameras
● Examples of TOF technique application in nuclear physics experiments at ATLAS: mass and nuclear charge identification of radioactive ions using gas-filled magnet
3PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
TOF systems
● High-power (hundreds of kilowatts) accelerators such as RIA driver linac Requirehigh-precisioncontrolofbeamenergy Maintainshortbunches(~40-100picoseconds)
● Beams of rare isotopes must be analyzed by detecting individual particles. Fast time measurements (~20 picoseconds resolution) are necessary to control bunched beam quality
● Absolute energy measurements based on TOF system Requiredformanyexperiments Non-destructive,cheapcomparedtomagnet Wellsuitedforbeamvelocities<0.5c Veryhighaccuracycanbeobtained Widerangeofbeamcurrentsstartingfrom~0.3nA(~1010
particles/sec)canbeanalyzed
4PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Absolute energy measurement using resonant TOF system
48.505 MHz
Beam frequency = 48.500 MHzResonator frequency =48.500 MHz
FEE
Phase meter
f=48.505-48.500 = 5 kHz
FEE FEE
5PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Absolute energy measurement using resonant TOF system
1 1 0 10 0 1
2 2 0 20 0 2
1/ 22 210 1
1 21 2 5 5
0
cos(( ) ) cos( )
cos(( ) ) cos( )
2 cos( )
52
482
rf beam b
rf beam b
b
b b kHz kHz
U U t U t
U U t U t
E A B AB t
kHz
MHz
0 2000 4000 6000 8000 1 104
1.5
1
0.5
0
0.5
1
1.51.3
1.3
E TV( )
1 1040 TV
0 2000 4000 6000 8000 1 104
0.4
0.2
0
0.2
0.40.5
0.5
EE TV( )
1 1040 TV
0 10 20 30 401
0.5
0
0.5
11
1
E1 TV( )
400 TV
6PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Absolute energy measurement using resonant TOF system
● Precision of TOF measurements: Signal–noiseratio Phasejitterduetovibration,somethermaleffects Majorcontribution–beamphasejitter
Phaseadvanceover9m–5400degof48.5MHz
Phasemeterprecision~0.2deg
TOF=300nsec
5
5 5
0.23.7 10
5400
3 10 3.7 10 10 picoseconds
t
t
t
● Accuracy of beam energy measurements:
Additionaleffectisthedistancebetweenthedetectors
TypicalnumberisE/E=210-4
7PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
High accuracy is achieved by using
● Chain of bunches, signal is integrated in the resonator (msec);
● Mixing of two frequencies in the resonator helps to avoid extra noise that can be accumulated in external circuits
● The bunch phase at 48.5 MHz is directly translated to 5 kHz and minimizes phase meter errors
● Front End Electronics Amplitudedetection Narrowband-passfilter(5kHz) AGC(automaticgaincontrol)amplifier
8PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Bunch Length detector
1-tangstin target wire, 2-collimator, 3-plates of the rf deflector, 4-MCP, 5-phosphor screen, 6-CCD camera,.
I()
Ion beam
, Z
Utarg Secondary electrons
I(X) X
1 2 3
)sin( tn2
UVV mstfoc
)sin( tn2
UVV mstfoc
9PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Electron beam trajectories with no RF applied (streak camera)
Target wire Electron beam trajectories
Collimator
Deflector plates
Potential contoursb)
a)
10PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Electron beam image on the phosphor with no RF applied
20 mm
100 200 300 400 500
0
5
10
15
20
25
intensity,rel.units
pixels
FocusedelectronbeamprofileResolutionis~15pixelsBunchwidth=10degat97MHz=290picoseconds15pixelscorrespondsto~10picosecondsresolution
11PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
RF on, bunch image
12PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Bunch time profile
● 58 Ni bunch profile (a) inferred from scintillator signal (b).
13PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Time resolution
● The time required for the emission of secondary electrons
● The time difference, due to the different arrival times of the secondary electrons originating from different points of the wire, at the rf deflector
● The contribution to the detector resolution from the angular and energy distributions of the secondary electrons
● The time of flight of the electrons through the electrostatic field of the plates.
● Finally the RF voltage and rf phase jitter is a very important factor in determining the time resolution of the detector.
14PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Improvement of time resolution of the existing BLD
● Reduce both the entrance and exit slits size down to ~0.2 mm;
● Use single electron mode of measurements. In the single electron mode the problem associated with the finite size of the SE beam will be minimized.
● Reduce the diameter of the wire to ~0.03 mm;
● Increase the voltage applied to the wire up to 15 kV;
● Increase the rf voltage to have large sweeping amplitude on the exit slit;
● Improve electron beam optics to obtain more isochronous trajectories;
● Improve phase jitter of the rf deflector by introducing an external RF synthesized signal generator with a high stability.
15PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Heavy-ion bunch time structure using X-rays
Streak camera
Focusingspectrographforpicosecondtimeresolutionofionbeam(adaptedfrom[1])
[1]O.N.Rosmejetal. 30th EPS Conference on Contr. Fusion and Plasma Phys., St. Petersburg, 7-11 July 2003 ECA Vol. 27A, O-1.9C
16PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Typical streak camera being used at electron synchrotronsTime resolution of streak cameras can be less than 1 picosecond
17PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Heavy-ion bunch time structure using X-rays (proposal)
● Ions penetrate the thin target ( 0.1-0.2 mm) and undergo multiple collisions with target atoms.
● Excitation of bound electrons followed by radiative decay gives rise to projectile and target radiation. Decay time ~10 femtosec
● Focusing specrograph with spatial resolution provides high spectral and spatial resolution of the K-shell spectra.
● Streak camera measures the temporal structure of the beam with picosecond resolution.
18PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
ATLAS Layout
19PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Mass and nuclear charge identification using gas-filled spectrograph
01
, ,
vC Zv
mvB
q
q Z e
C are parameters
Difficulty:a) The masses are very closeb) The same q/m, velocity
20PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
TOF for mass and charge identification
21PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Time-of-Flight Measurement with the Storage Ring in the Isochronous Mode (Milan Matos’ presentation)
In jectionIn jectionIn jection
time[ s]
U[V ]
0 1 2
0
-0.5
time[ s]
U[V ]
0 1 2
0
-0.5
23PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Time-of-Flight Spectrum
0
100
200
300
400
500
600
700
496 498 500 502 504 506 508 510 512 514Revolutiontime[ns]
Intensity
103Zr39+
0
5
10
15
20
25
30
35
507.6 507.7 507.8 507.9 508 508.1 508.2
135Te
51+
90Se
34+
127Cd
48+
82Ga
31+
119Rh
45+
111Tc
42+
103Y39+
111Mo
42+
90Br
34+
127In
48+
119Pd
45+
37Si14+
Intensity
revolutiontime[ns]
red-nuclidewithunknownmassblue-nuclidewithknownmass
24PioneeringScience andTechnology Pico-Sec Timing Hardware Workshop, November 18, 2005
Conclusion
● Time resolution of 3-5 picoseconds is required to tune and operate high-power heavy-ion linacs
● So far the technique remains complex and expensive to provide high resolution
● TOF is a common technique for identification of mass and nuclear charge of rare isotopes. Currently several large facilities are being constructed worldwide to produce beams of exotic nuclei.
● High resolution MCPs can help to reduce the cost of storage rings or spectrographs in future rare isotope accelerator facilities