design note tri-dn-16-07 ariel...

Document-129911

Design Note TRI-DN-16-07ARIEL Pre-separator

Document Type: Design note

Release: 03 Release Date: 2018–04–27

Authors: S. Saminathan, R. Baartman

Name: Signature:

Authors:S. Saminathan

APPROVAL RECORD

R. Baartman

Reviewed By:

M. Marchetto

F. Ames

A. Gottberg

Approved By: O. Kester

Note: Before using a copy (electronic or printed) of this document you mustensure that your copy is identical to the released document, which is stored onTRIUMF’s document server.

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ARIEL Pre-separator

Document-129911 Release No. 03 Release Date: 2018–04–27

History of Changes

Releasenumber

Date Description of changes Authors

1 to 2 Link to version history

03 2018–04–27 Update on the optics design ofthe pre-separator matching sec-tions in order to accommodatethe first doublet within the avail-able space in the first targetmodule. Shim for the electro-static bender (EB1) is proposed.

S. SaminathanR. Baartman

Keywords: Pre-separator, Preseparator, Mass separator, Nier separator, RIBtransport, ARIEL Pre-separator, ARIEL LEBT

Distribution List: Reviewer, Approver, C. Barquest, J. Chak, P. Dirksen,E. Guetre, J. Lassen, B. Laxdal, A. Messenberg, N. Muller, B. Paley, A. Per-era, D. Preddy, D. Rowbotham

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ARIEL Pre-separator


Abstract

A pre-separator has been designed to achieve a mass resolving powerof 300 for the ARIEL RIB transport. The pre-separator consists of amagnetic and an electrostatic bender, which allows an achromatic modeof operation. In this design note the beam optics design, beamline layout,element specifications and diagnostic requirements are documented.

1 Introduction

The pre-separator beamline will be used to transport the extracted beam fromARIEL target ion source to the mass separator room. Also it is used to pre-select the required ions. This allows us to minimize the radioactive contam-ination outside the target hall, i.e. before transporting the beam into themass separator room. This beamline consists of a magnetic and an electro-static bender for momentum and energy separation. A schematic layout of theARIEL pre-separator is shown in Fig. 1. ARIEL facility consist of two targetion sources called as Ariel Proton Target West (APTW) and Ariel ElectronTarget East (AETE) [1]. Each target ion source will be provided with its ownpre-separator and both are optically identical.

In this design note the optics calculations for the pre-separator is presentedin Sec. 3. The requirements of the bending magnet are briefly described inSec. 3.1 while a detail design requirement for the magnet can be found in theRef. [2]. A detailed design of the electrostatic bender is described in Sec. 3.2.The optical elements in the beamline are tabled in table 5. Finally, the toler-ances for the optical elements are described in Sec. 4.

1.1 Purpose and scope

Purpose of this design note is to provide some basic information about thefunctionality of the pre-separator. Scope of this document is to present thebeam optics design of the pre-separator.

1.2 Definitions

• Coordinate system:The Cartesian coordinate system defined herein issuch that the origin is in the center of cyclotron, +X points to East, +Ypoints to North, and +Z points upward.

• Source slit (COL8A): A collimator is used in the matching section (upstreamof the pre-separator) to define the size and position of incoming beamsinto the pre-separator.

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ARIEL Pre-separator


• Mass slit (SLIT8B): A set of slits are used in the pre-separator (downstreamto the magnetic bender) to select the required m/q.

• Energy slit (SLIT19): A set of slits are used in the beamline (downstreamto the first periodic section or third periodic section) to limit the energyacceptance.

1.3 Abbreviations

• ARIEL: Advanced Rare IsotopE Laboratory

• RIB: Rare Isotope Beam

• LEBT: Low Energy Beam Transport

• EQ: Electrostatic Quadrupole

• MB: Magnetic Bender

• MB-EFB: Magnetic Bender’s Effective Field Boundary

• EB: Electrostatic Bender

• EB-EFB: Electrostatic Bender’s Effective Field Boundary

• HRS: High Resolution Separator

• ATS: Ariel Target Station

• APTW: Ariel Proton Target West

• AETE: Ariel Electron Target East

• ALTW: Ariel Lower level Transport West

• ALTE: Ariel Lower level Transport East

• FC: Faraday Cup

• COL: COLlimator

• PM: Profile Monitor

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ARIEL Pre-separator


2 Optics requirements

Basic requirements for the beam optics design is given in table. 1. A detailedrequirements for the pre-separator is given in ref. [3, 4].

Maximal beam energy (E) 60 keV

Maximum beam rigidity (Bρ)max 0.544 Tm

First bending angle of the beamline (θB) 112◦

Second bending angle of the beamline (θE) -90◦

Mode of operation achromatic

Emittance [4*RMS] (ε) 20µm

Mass resolving power (M/∆M) 300

Table 1: Requirements for the ARIEL pre-separator.

3 Pre-separator

A schematic layout of the pre-separator beamline is shown in Fig. 1 and thelayouts for both target stations (AETE and APTW) are identical. The ARIELpre-separator consists of an electrostatic and a magnetic dipole element. Italso contains quadrupole elements in between the dipoles. The electrostaticbend compensates the energy dispersion of the magnetic bend. This allowsan achromatic mode of operation resulting in a high mass resolving power forbeams with a high energy spread. Other advantages in the pre-separator designwith an achromatic mode: a) It allows rejection of neighbouring masses thatare off energy, as can happen when a much more populous undesired isotope isstripped in the extraction region and gains less energy than the total potentialdifference, b) It has an energy collimation feature, c) The achromaticity willcancel energy-horizontal motion correlation and hence it simplifies tuning whensmall energy changes are being made.

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ARIEL Pre-separator


-2400 -2200 -2000 -1800 -1600 -1400 -1200

X (cm)

5900

6000

6100

6200

6300

6400

6500

6600

6700

6800

6900

Y (

cm

)

APTW AETE

EB1MB0 MB0

Target hall north wall

Mass separator room

N

EW

ALTEALTW

Target hall

Periodic sec.

Matching sec.

Pre-separator

EB1

COL8A COL8A

SLIT8B SLIT8B

Figure 1: Layout of the pre-separator in the target hall.

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ARIEL Pre-separator



Horizontal half width of the beam [2*RMS] (x) 1.28 mm

Horizontal half width of the beam divergence [2*RMS] (x′) 15.6 mrad

Vertical half width of the beam [2*RMS] (y) 4.2 mm

Vertical half width of the beam divergence [2*RMS] (y′) 4.8 mrad

Correlation parameter in horizontal plane (r12) 0.0

Correlation parameter in vertical plane (r34) 0.0

Emittance [4*RMS] (ε) 20µm

Table 2: Initial beam parameters for the pre-separator at the location of COL8A (seeFig. 1).

The beam optics simulations were performed by using our in-house codeTRANSOPTR and the final design of the pre-separator has been bench-markedwith the code COSY INFINITY [6] and GIOS [7] up to third-order.

The initial beam parameters at the location of the source slit (COL8A) isgiven in table 2. Figure 2 shows the calculated ion trajectories through thebeamline for three different masses with a mass difference of δm = ± 0.33 %. Inthe case of an extraction voltage of 60 keV, we have assumed an energy spreadof 10 eV (i. e., δE = ± 0.0083 %). The calculated beam envelope and energydispersion in the pre-separator by using the code TRANSOPTR is shown Fig. 3.

SLIT8B (see Fig. 2) is the image of COL8A with a magnification of 1 andthe mass dispersion is around 0.77 m. Also PM13 is a image of COL8A with amagnification around 1 and the energy dispersion is vanished at this location.In order to select a required m/q an adjustable slit (width) will be installed atthe location of the first focal point (SLIT8B), which is around 0.52 m down-stream to the exit effective field boundary (MB-EFB) of the bending mag-net (see Fig. 2 or 3). Figures 4 and 5 show the calculated spacial distribu-tions at the location of SLIT8B for a 60 keV beam with δE = ± 0.0083 % andδm = ± 0.33 % by using the code COSY INFINITY. A mass resolving powerabout 300 is achieved with ε = 20µm (see Fig. 4) and a mass resolving powerabout 420 is achieved with ε = 10µm (see Fig. 5).

Unique feature of the ARIEL pre-separator is its Nier like mass separatorconfiguration with the combination of electrostatic and magnet benders. This

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ARIEL Pre-separator


provides a higher mass resolution (δm ≈ ± 0.33 %) at the location of PM3 fora beam even with higher energy spread (δE > ± 0.0083 %). For an examplea beam with energy spread about 200 eV at 60 keV is difficult to resolve (seeFig. 6) at the mass selection slit (SLIT8B), whereas this is still possible toresolve (see Fig. 7) at the energy selection slit (i. e., location of PM3). It alsocan be resolved in the other locations of the beamline, i. e., by using a sliteither downstream to the first periodic section (see Fig. 8 at SLIT19) or thethird periodic section from the pre-separator exit matching section. Calculatedion trajectories on the straight optical axis are shown in Fig. 9.

In the linear approximation:

1. Mass resolving power at the location of mass slit (SLIT8B),

Rm =(x|δm)

2(x|x)W≈ 300 (1)

where (x|δm) = 0.77 m is the mass dispersion,(x|x) = 1.0 is the magnification, andW = 1.28× 10−3 m is the half width of the source slit (COL8A).

2. Energy resolving power at the location of energy slit (PM13 or SLIT19),

RK =(x|δE)

2(x|x)W≈ 327 (2)

where (x|δE) = 0.77 m is the energy dispersion,(x|x) = 0.92 is the magnification, andW = 1.28× 10−3 m is the half width of the source slit (COL8A).

Figure 10 and 11 show the calculated phase-space distributions (up to 3rdorder) at the location of PM13 for various beam emittances. These calculationsshows that the emittance growth will be less than 1 % in both horizontal andvertical planes for an initial beam emittance of 20µm. If we assume an initialemittance of 80µm then the emittance growth will about 3 % in the horizontalplane and 7 % in the vertical plane. Higher order aberrations could be mini-mized further by increasing the radius of the EB and/or increasing the distancebetween the MB and EB but in our case these are limited because of the craneaccessibility in the ARIEL target hall. The pre-separator layout is a trade-offbetween the aberrations and space constraint in the ARIEL target hall.

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ARIEL Pre-separator


EQ9 EQ10 EQ11 EQ12

EQ13

EB1

MB0

Massslit (SLIT8B)

Energy slit(PM13)

COL8A

Figure 2: Pre-separator layout with ion trajectories (60 keV, 2381+). Other possiblelocation for the energy selection slit is downstream to the first or third periodic section.

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ARIEL Pre-separator


-2

-1.5-1

-0.5 0

0.5 1

1.5 2

0 0

.5 1

1.5

2 2

.5 3

3.5

4

FC-PM-COL8AY8A

Y11

MB0-ent.

MB0

MB0-exit

FC-PM-SLIT8B

EQ9

EQ10

EQ11

PM11

EQ12

EB1-ent.

EB1

EB1-exit

EQ13

FC-PM13

dis

tan

ce (

m)

x-e

nv

elo

pe

(cm

)y

-en

vel

op

e (c

m)

En

erg

y d

isp

ersi

on

(m

)M

ass

dis

per

sio

n (

m)

foca

l p

ow

er (

arb

.)

Figure 3: Calculated beam envelope (2*RMS) with energy and mass dispersion for 60 keVion beam through the pre-separator with ε = 20µm.

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ARIEL Pre-separator


-8 -4 0 4 8

x (mm)

-8

-4

0

4

8

y (

mm

)

δm

= -0.33 %

δm

= -0.0 %

δm

= 0.33 %

Figure 4: Calculated spacial distributions at the location of SLIT8B (see Fig. 2 or 3) for a60 keV beam with ε = 20µm, δE = ± 0.0083 % and δm = ± 0.33 % by using the code COSYINFINITY.

-8 -4 0 4 8

x (mm)

-8

-4

0

4

8

y (

mm

)

δm

= -0.33 %

δm

= -0.0 %

δm

= 0.33 %

Figure 5: Calculated spacial distributions at the location of SLIT8B (see Fig. 2 or 3) for a60 keV beam with ε = 10µm, δE = ± 0.0083 % and δm = ± 0.33 % by using the code COSYINFINITY.

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ARIEL Pre-separator


TITLE OF GIOS INPUT: ARIEL-Presep-Feb2017 ;

DATE: Fri Feb 3 14:33:22 PST 2017

DEFINITION OF THE INITIAL PHASE SPACE

X = +/- 1.280E-03 LLU

A = +/- 1.563E-02 RAD

DM = 3.300E-03 *100%

DK = 3.300E-03 *100%

Y = +/- 4.200E-03 TLU

B = +/- 4.760E-03 RAD

0 2 2 - 4 4 - 6 6 -

0

2

2 -

4

4 -

6

6 -

PLOT OF [ X vs. Y ] AT Z = 2.017E+00 LLU

SIZE OF WINDOW

X = +/- 6.000E-03 TLU

Y = +/- 6.000E-03 TLU

STATISTICAL INFORMATIONS

NUMBER OF STARTED PARTICLES: 500000

NUMBER OF ARRIVED PARTICLES: 500000 [ 100.0 %]

NUMBER OF COUNTED PARTICLES: 499926 [ 100.0 %]

Figure 6: Calculated spatial profiles at the location of SLIT8B for a 60 keV beam withε = 20µm, δE = ± 0.33 % and δm = ± 0.33 % by using the code GIOS.

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ARIEL Pre-separator



DATE: Fri Mar 24 10:20:23 PDT 2017


X = +/- 1.280E-03 LLU

A = +/- 1.563E-02 RAD

DM = 3.300E-03 *100%

DK = 3.300E-03 *100%

Y = +/- 4.200E-03 TLU

B = +/- 4.760E-03 RAD

0 2 2 - 4 4 - 6 6 -

0

2

2 -

4

4 -

6

6 -


SIZE OF WINDOW

X = +/- 6.000E-03 TLU

Y = +/- 6.000E-03 TLU





Figure 7: Calculated spatial profiles at the location image location downstream to theEB1 (at PM13) for a 60 keV beam with ε = 20µm, δE = ± 0.33 % and δm = ± 0.33 % byusing the code GIOS.

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ARIEL Pre-separator



DATE: Fri Mar 24 10:20:23 PDT 2017


X = +/- 1.280E-03 LLU

A = +/- 1.563E-02 RAD

DM = 3.300E-03 *100%

DK = 3.300E-03 *100%

Y = +/- 4.200E-03 TLU

B = +/- 4.760E-03 RAD

0 2 2 - 4 4 - 6 6 -

0

2

2 -

4

4 -

6

6 -


SIZE OF WINDOW

X = +/- 6.000E-03 TLU

Y = +/- 6.000E-03 TLU





Figure 8: Calculated spatial profiles at the location of SLIT19 for a 60 keV beam withε = 20µm, δE = ± 0.33 % and δm = ± 0.33 % by using the code GIOS.

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ARIEL Pre-separator


Y

X

Y-MAX = +/- .050 TLU

X-MAX = +/- .050 TLU

Z-MAX = 5.799 LLU

Z-MAX = 5.799 LLU

Figure 9: Calculated ion trajectories for a 60 keV beam with ε = 20µm, δE = ± 0.33 % andδm = ± 0.33 % by using the code GIOS.

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ARIEL Pre-separator


-10 -5 0 5 10mm

-40

-30

-20

-10

0

10

20

30

40

mra

d

x-Px

ǫ = 80 µ mǫ = 40 µ mǫ = 20 µ m

Figure 10: Calculated phase-space for various beam emittances in the horizontal plane atthe location of PM13 (see Fig. 2 or 3) for a 60 keV beam by using the code COSYINFINITY.

-10 -5 0 5 10mm

-40

-30

-20

-10

0

10

20

30

40

mra

d

y-Py

ǫ = 80 µ mǫ = 40 µ mǫ = 20 µ m

Figure 11: Calculated phase-space for various beam emittances in the vertical plane at thelocation of PM13 (see Fig. 2 or 3) for a 60 keV beam by using the code COSY INFINITY.

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ARIEL Pre-separator


3.1 Magnetic bender

A 112◦ dipole magnet bender with bending radius of 500 mm is used in the Pre-separtor for the momentum selection at the location of SLIT8B. The magneticbender provides a mass dispersion of 770 mm, which yields a mass resolvingpower of 300. The magnetic bender has an acceptance of 300µm. The basicrequirements of this bender is given in table 3. A detailed design requirementsis presented in ref. [2].

Figure 12 and 13 show the calculated phase-space distributions (up to 3rdorder) at the location of SLIT8B for various beam emittances. These calcula-tions shows that the maximum emittance growth will be less than 1 % in thehorizontal plane and less than 0.1 % in the vertical plane for an initial beamemittance of 20µm. If we assume an initial emittance of 80µm then the max-imum emittance growth will be about 3 % in the horizontal plane and 0.1 % inthe vertical plane because of the second-order aberration.

Magnet type Rotated pole face

Bending angle (θ) 112◦

Pole face rotation angle (entrance and exit) 27.5◦

Bending radius (ρ) 500 mm

Pole (full) gap (Non-bend plane) 60.0 mm

Maximum magnetic rigidity (Bρ) 0.5576 Tm

Maximum field strength (Bmax) ≥ 1.1152 T

Field homogeneity (∆∫Bdl)/(

∫Bdl) ≤ 6× 10−4

Table 3: Summary of the basic magnet requirements.

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ARIEL Pre-separator


-10 -5 0 5 10mm

-40

-30

-20

-10

0

10

20

30

40

mra

d

x-Px

ǫ = 80 µ mǫ = 40 µ mǫ = 20 µ m

Figure 12: Calculated phase-space for various beam emittances in the horizontal plane atthe location of SLIT8B (see Fig. 2 or 3) for a 60 keV beam by using the code COSYINFINITY.

-10 -5 0 5 10mm

-40

-30

-20

-10

0

10

20

30

40

mra

d

y-Py

ǫ = 80 µ mǫ = 40 µ mǫ = 20 µ m

Figure 13: Calculated phase-space for various beam emittances in the vertical plane at thelocation of SLIT8B (see Fig. 2 or 3) for a 60 keV beam by using the code COSY INFINITY.

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ARIEL Pre-separator


3.2 Electrostatic bender

A 90◦ toroidal electrostatic bender (EB) is used in the pre-separator to com-pensate the energy dispersion due to the magnetic bender (MB). In order tohave a focusing in the non-bend plane, the bender electrodes are curved in thethat plane. The ratio of the electrode radius in the bend plane to the non-bend plane is 0.5. The bender has an acceptance of 250µm. The other basicrequirements of this bender are given in table 4. Figure 14 and 15 show theelectrostatic bender layout in the horizontal and vertical plane, respectively.Figure 15 shows electrodes with the proposed shim in order to improve thefield flatness in the vertical plane. A detail study on the dipoles with a shim ispresented in Ref. [10].

A quadrupole is added at each end of the electrostatic bender for edge fo-cusing. In our case the electrostatic bender with additional quadrupole opticsgives a magnification around 1. The electrostatic bender is modeled with thecode OPERA3D. Figure 17 shows the optimized electrode height for a smoothequipotential contour around the corner of the electrostatic bender in the verti-cal plane. In our model the effective field boundary (EFB)(see Fig. 18) has beenoptimized by adjusting the skimmer electrode’s aperture size and the skimmerelectrode 16 position with respect to the bender’s electrode.

The calculated field map is imported into the code COSY for beam trans-port study through the electrostatic bender [9]. Figure 19 shows the calculatedcentral ion trajectory (60 keV, 2381+) through the electrostatic bender for atotal distance of 0.8 m from the bender center. Figure 20 shows the potentialalong this trajectory computed by the code COSY. The potential seen by theion trajectory is about 0.5 % of the applied potential to the electrode and thisis around the entrance and exit locations of the bender (see fig. 20). Figures 21and 22 show the calculated phase-space (up to 3rd order) at the location ofPM13 for various beam emittances. These calculations shows that the maxi-mum emittance growth will be less than 3 % in the horizontal plane and lessthan 0.5 % in the vertical plane for an initial beam emittance of 20µm. If weassume an initial emittance of 80µm then the maximum emittance growth willbe about 10 % in the horizontal plane and 1 % in the vertical plane because ofthe second-order aberration.

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ARIEL Pre-separator


Bender type Toroidal bender

Bending angle (θ) 90◦

Electrode face rotation angle (entrance and exit) 0◦

Bending radius (ρ) 450 mm

Electrode (full) gap in the bend plane 50 mm

Maximum voltage on the electrode ±7 kV

Table 4: Summary of the basic electrostatic bender requirements.

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ARIEL Pre-separator


90°

95°

R45

0

R400

R425

R475

R500

40

1

87°

Skimmer plateHV Electrode

Skimmer plate

Figure 14: Cross section view of the 90◦ electrostatic bender in the bend plane (x). Thedash line at either side of the bender shows the EFB of the bender.

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ARIEL Pre-separator


14,0°

R875R900

R925

0,3°

45,0

°

R5

R1

100

Figure 15: Cross section view of the 90◦ electrostatic bender’s electrode in the non-bendplane (y) shown with the proposed shim.

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ARIEL Pre-separator


16°

R880

R920R900

165

R1

Figure 16: Cross section view of the 90◦ electrostatic bender’s skimmer plate in thenon-bend plane (y).

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ARIEL Pre-separator


Figure 17: Equipotential contour at the center of the electrostatic bender in the verticalplane.

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ARIEL Pre-separator


0 0.1 0.2 0.3 0.4 0.5 0.6

[m]

0

0.05

0.1

0.15

0.2

0.25

0.3

[MV

/m]

|E|

Electrode edge

Effective length

Skimmer

Figure 18: Calculated total electrostatic field (|E|) along the beamline axis (from the bendercenter to exit) of the 90◦ electrostatic bender.

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ARIEL Pre-separator


0 500 1000

[mm]

-200

0

200

400

600

[mm

]

Figure 19: Calculated central ion trajectory (60 keV, 2381+) through the electrostaticbender by using the code COSY INFINITY.

0 500 1000

[mm]

-0.12

-0.1

-0.08

-0.06

-0.04

-0.02

0

0.02

[kV

]

Figure 20: Calculated potential along the central trajectory (see fig. 19) by using the codeCOSY INFINITY.

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ARIEL Pre-separator


-15 -10 -5 0 5 10 15

x (mm)

-50

-40

-30

-20

-10

0

10

20

30

40

50

xp (

mra

d)

80 m40 m

20 m

Figure 21: Calculated phase-space for various beam emittances in the horizontal plane atthe location of exit EB-EFB (see Fig. 14) for a 60 keV beam by using the code COSYINFINITY.

-15 -10 -5 0 5 10 15

y (mm)

-50

-40

-30

-20

-10

0

10

20

30

40

50

yp (

mra

d)

80 m40 m

20 m

Figure 22: Calculated phase-space for various beam emittances in the vertical plane at thelocation of exit EB-EFB (see Fig. 14) for a 60 keV beam by using the code COSYINFINITY.

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ARIEL Pre-separator


Name Pot. [kV] R [mm] L [mm] S [mm] X [mm] Z [mm] Y [mm] θ [deg.]

FC-PM-COL8A - - - 0.00 -14027.33 10.50 62568.24

Y8A - - - 50.00 -14046.06 10.50 62614.60

MB0-ent. - - - 519.75 -14222.03 10.50 63050.16

MB0 - - - 1008.45 -14172.96 10.50 63517.05 112◦

MB0-exit - - - 1497.14 -13758.44 10.50 63737.46

FC-PM-SLIT8B - - - 2016.89 -13238.69 10.50 63737.46

Y8B - - 2152.03 -13103.54 10.50 63737.46

EQ9 6.308 25.4 50.8 2232.51 -13023.07 10.50 63737.46

EQ10 -2.741 25.4 126.2 2390.30 -12865.28 10.50 63737.46

EQ11 6.308 25.4 50.8 2548.08 -12707.49 10.50 63737.46

PM11 - - - 2763.70 -12491.87 10.50 63737.46

Y11 - - - 2877.07 -12378.50 10.50 63737.46

EQ12 -1.278 25.4 50.8 2925.15 -12330.42 10.50 63737.46

EB1-EFB-ent. - - - 3047.56 -12208.00 10.50 63737.46

EB1 - - - 3400.99 -11889.81 10.50 63869.26 90◦

EB1-EFB-exit - - - 3754.42 -11758.00 10.50 64187.46

EQ13 -1.278 25.4 50.8 3876.84 -11758.00 10.50 64309.87

FC-PM13 - - - 4038.29 -11758.00 10.50 64471.32

Table 5: The reference coordinates (X, Y, Z) corresponds to the location of the mid-point ofthe each optical element and diagnostic device in the AETE pre-separator (see fig. 3). The2nd column (pot.) specifies the quadrupole strength in kV for 60 keV ion beam. The 3rd and4th column specifies the radius (R) and length (L) of the quadrupole in millimeter. The 5thcolumn (S) is the reference trajectory length in millimeter. The 9th column (θ) specifies thebending angle of the magnetic (MB) and electrostatic (EB) benders.

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ARIEL Pre-separator


3.3 Matching sections

The ARIEL pre-separator beamline consists of two matching sections one atthe entrance and another one at the exit of the pre-separator (see Fig.1). Thematching section at the entrance is designed in such a way that the incomingbeams from the ARIEL target ion source to the pre-separator are matched atthe location of object point of the pre-separator dipole. This section consistsof four electrostatic doublets and the calculated beam envelope through thissection is shown in Fig. 23 and Fig. 24 with ε = 4µm and ε = 20µm, respec-tively. This section is optically very flexible to obtain many different tuneswith various quadrupole configurations. Initial beam parameters for this sec-tion is obtained from the extraction simulations presented in Ref. [11]. Beamacceptance of this section about 100µm.

The other matching section is located at the exit of the pre-separator, i. e.,downstream to the 90◦ electrostatic bender. This section connects the pre-separator with the periodic section in the RIB beamline (see Fig. 1). Fourelectrostatic quadrupoles in this section are used to the match the outgoingbeam into the proceeding periodic section and the calculated beam envelope isshown in Fig. 25. Beam acceptance of this section about 250µm.

Required beam diagnostics [8] and the optical elements for the entrance andthe exit matching section are tabled in table 7 and 8, respectively.


Horizontal half width of the beam [2*RMS] (x) 1.2 mm

Horizontal half width of the beam divergence [2*RMS] (x′) 5.9 mrad

Vertical half width of the beam [2*RMS] (y) 1.2 mm

Vertical half width of the beam divergence [2*RMS] (y′) 5.9 mrad

Correlation parameter in horizontal plane (r12) 0.7769

Correlation parameter in vertical plane (r34) 0.7769

Emittance [4*RMS] (ε) 4.4µm

Table 6: Initial beam parameters at the exit of the ground electrode in the extractionsystem of ARIEL target ion source presented in Ref. [11].

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ARIEL Pre-separator


-2

-1.5-1

-0.5 0

0.5 1

1.5 2

0 0

.5 1

1.5

2 2

.5 3

3.5

Origin

Beam start

XY0

EQ1

EQ2

FC-PM2

XY2

EQ3

EQ4

PM4

XY4

EQ5

EQ6

PM6

XY6

EQ7

EQ8

FC-PM-COL8A

dis

tan

ce (

m)

x-e

nv

elo

pe

(cm

)y

-en

vel

op

e (c

m)

foca

l p

ow

er (

arb

.)

Figure 23: Calculated beam envelope (2*RMS) for a 60 keV ion beam through the matchingsection at the entrance of pre-separator with ε = 4µm( For the emittance see Ref. [11]).

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ARIEL Pre-separator


-2

-1.5-1

-0.5 0

0.5 1

1.5 2

0 0

.5 1

1.5

2 2

.5 3

3.5

Origin

Beam start

XY0

EQ1

EQ2

FC-PM2

XY2

EQ3

EQ4

PM4

XY4

EQ5

EQ6

PM6

XY6

EQ7

EQ8

FC-PM-COL8A

dis

tan

ce (

m)

x-e

nv

elo

pe

(cm

)y

-en

vel

op

e (c

m)

foca

l p

ow

er (

arb

.)

Figure 24: Calculated beam envelope (2*RMS) for a 60 keV ion beam through the matchingsection at the entrance of pre-separator with ε = 20µm

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ARIEL Pre-separator


-2

-1.5-1

-0.5 0

0.5 1

1.5 2

0 0

.2 0

.4 0

.6 0

.8 1

1.2

1.4

1.6

1.8

FC-PM13

Y13

EQ14

EQ15

EQ16

EQ17

PM17

XY17

EQ18

EQ19

FC-SLIT19

dis

tan

ce (

m)

x-e

nv

elo

pe

(cm

)y

-en

vel

op

e (c

m)

foca

l p

ow

er (

arb

.)

Figure 25: Calculated beam envelope (2*RMS) for a 60 keV ion beam through the matchingsection at the exit of pre-separator with ε = 20µm.

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ARIEL Pre-separator


Name Pot. [kV] R [mm] L [mm] S [mm] X [mm] Z [mm] Y [mm]

Origin - - - 0.00 -12780.00 10.50 59481.00

beam start - - - 431.00 -12941.46 10.50 59880.62

XY0 - - - 503.25 -12968.52 10.50 59947.61

EQ1 -2.683 19.05 38.10 602.30 -13005.62 10.50 60039.45

EQ2 2.683 19.05 38.10 700.25 -13042.32 10.50 60130.27

FC-PM2 - - - 989.01 -13150.49 10.50 60398.00

XY2 - - - 1178.72 -13221.55 10.50 60573.89

EQ3 -3.349 25.40 50.80 1284.12 -13261.04 10.50 60671.62

EQ4 3.349 25.40 50.80 1424.92 -13313.78 10.50 60802.17

PM4 - - 1752.24 -13436.40 10.50 61105.65

XY4 - - 1904.16 -13493.31 10.50 61246.51

EQ5 -3.349 25.40 50.80 2009.56 -13532.79 10.50 61344.23

EQ6 3.349 25.40 50.80 2150.36 -13585.54 10.50 61474.78

PM6 - - 2465.47 -13703.58 10.50 61766.95

XY6 - - 2635.17 -13767.15 10.50 61924.30

EQ7 -2.961 25.40 50.80 2740.57 -13806.64 10.50 62022.02

EQ8 3.179 25.40 50.80 2881.37 -13859.38 10.50 62152.57

FC-PM-COL8A - - - 3329.69 -14027.32 10.50 62568.25

Table 7: The reference coordinates (X, Y, Z) corresponds to the location of the mid-pointof the each optical element and diagnostic device in the beamline between the AETE targetion source and the AETE pre-separator beamline (see fig. 23). Origin is the cross-over pointbetween the driver beam and RIB beam. Beam start is the location where the phase-spaceis defined after the ion beam extraction (see Table 6). The 2nd column (pot.) specifiesthe quadrupole strength in kV for 60 keV ion beam. The 3rd and 4th column specifies theradius (R) and length (L) of the quadrupole in millimeter. The 5th column (S) is the referencetrajectory length in millimeter.

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ARIEL Pre-separator


Name Pot. [kV] R [mm] L [mm] S [mm] X [mm] Z [mm] Y [mm]

FC-PM13 - - - 00.00 -11758.01 10.50 64471.32

Y13 - - - 60.00 -11758.01 10.50 64531.32

EQ14 -2.467 25.40 50.80 145.40 -11758.01 10.50 64616.72

EQ15 2.923 25.40 76.20 285.10 -11758.01 10.50 64756.42

EQ16 -2.275 25.40 50.80 424.80 -11758.01 10.50 64896.12

EQ17 2.044 25.40 50.80 603.60 -11758.01 10.50 65074.92

PM17 - - - 760.60 -11758.01 10.50 65231.92

XY17 - - - 832.20 -11758.01 10.50 65303.52

EQ18 -2.026 25.40 50.80 917.60 -11758.01 10.50 65388.92

EQ19 2.026 25.40 50.80 1603.60 -11758.01 10.50 66074.91

SLIT19 - - - 1760.60 -11758.01 10.50 66231.91

Table 8: The reference coordinates (X, Y, Z) corresponds to the location of the mid-pointof the each optical element and diagnostic device in the beamline at the exit of the AETEpre-separator beamline (see fig. 25). The 2nd column (pot.) specifies the quadrupole strengthin kV for 60 keV ion beam. The 3rd and 4th column specifies the radius (R) and length (L)of the quadrupole in millimeter. The 5th column (S) is the reference trajectory length inmillimeter.

4 Tolerances

The integrated field along the beam path must be no larger than about 80 gauss cm.The local ambient field bumps should be less than 0.8 gauss. Mechanical andelectrical tolerances (see Table 9) for the optical elements are calculated accord-ing to the guidelines given in reference [12].

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ARIEL Pre-separator


Element V [kV] f [mm] x [mm] θ [mrad] ∆x [mm] ∆z [mm] ∆V [volts]

EQ1 – EQ8 3.676 207.3 15.4 69.6 0.21 1.0 3.0

EQ9 – EQ13 6.308 121.0 5.8 24.7 0.12 8.2 23.0

EQ14 – EQ17 2.927 173.6 9.0 40.3 0.17 3.1 6.0

EB 90◦ 6.944 191.0 14.3 31.5 0.2 5.0 1.0

MB 112◦ [2] 1.1152 T 960.0 23.1 24.7 1.0 8.2 5.0 G

Table 9: Mechanical and electrical tolerances of the pre-separator elements (for ε = 50µm).V is the maximum voltage of the element (for 60 keV beam). f , x, θ are focal length, beam(half-)size and beam (half-)divergence, respectively. ∆x, ∆z, and ∆V are tolerances fortransverse position, longitudinal position and voltage. The roll angle of the elements shouldbe less than 1 mrad.

5 Summary

Beam optics design for the ARIEL pre-separator has been done to achievea mass resolving power of 300 for a given emittance of 20µm at an extrac-tion potential of 60 kV. The pre-separator can be operated at an achromaticmode with the specified beam optics. Beam optics calculations also includesthe matching section at the entrance and exit of the pre-separator beamline.Optical elements and its design details are presented.

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ARIEL Pre-separator


References

[1] M. Marchetto, and S. Saminathan, ARIEL Front-End Design Note,Document-41767, Internal report, TRIUMF, June, 2015.

[2] S. Saminathan, and N. Muller, Dipole magnet requirements for the ARIELpre-separator, Document-129912, Internal report, TRIUMF, April, 2016.

[3] M. Marchetto, ARIEL Pre-separator Requirements, Document-124001, In-ternal report, TRIUMF, Jan., 2016.

[4] M. Marchetto, ARIEL-II RIB Transport System Requirements, Document-123559, Internal report, TRIUMF, Dec., 2015.

[5] J.A. Maloney, and M. Marchetto, ARIEL High Resolution Separator,Document-109442, Internal report, TRIUMF, July, 2015.

[6] M. Bertz et al.,, COSY INFINITY Version 8.1, see http://cosy.pa.msu.edu.

[7] H. Wollnik et al., Nucl. Instr. and Meth. A 258 (1987) 408.

[8] S. Saminathan, M. Marchetto, and C. Barquest, Diagnostics requirementsfor the ARIEL Low Energy Beam Transport, Document-121991, Internalreport, TRIUMF, Sep., 2015.

[9] J.A. Maloney, et al., Electrostatic potential map modeling with COSY Infin-ity, Nucl. Instr. and Meth. in Phy. Res. Section B: Beam Interactions withMaterials and Atoms, Dec., 2015.

[10] T. Planche, M.J. Basso, P.M. Jung, S. Saminathan, and R. Baartman,Conformal Mapping Approach to Dipole Shim Design, 2018, arXiv preprintarXiv:1801.05470.

[11] F. Maldonado, ARIEL Target Ion Source Beam dynamics, TRI-DN-17-07,Internal report, TRIUMF, March, 2017.

[12] R. Baartman, Tolerances in the LEBT Optics, TRI-DN-97-11, Internalreport, TRIUMF, Nov., 1996.

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