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