ZQNA Electrostatic Quadrupoles for ELENA Transfer Lines

1. Conceptual design2. Performance3. Engineering details4. Interfaces5. Production planning

D. Barna, W. Bartmann, P. Moyret, R. Ostojic, J-F. Poncet IIC, 31 July 2014

Documentation

Engineering Specification:

Mechanical drawings in CDD under “AD_ZQNA%”.

ENGINEERING SPECIFICATION

ELECTROSTATIC QUADRUPOLE ASSEMBLY (ZQNA) FOR ELENA TRANSFER LINES

ABSTRACT:

The ELENA transfer lines use electrostatic elements to guide and deliver the beam to the experiments. This document describes the design and performance of the electrostatic quadrupole assembly (ZQNA), which contains two quadrupoles and one horizontal and one vertical corrector, mounted in a common vacuum chamber. About 60 assemblies will be used in the ELENA transfer lines.

Functional requirements - 1 Strength

– Quadrupoles: 6 m-1 (100 keV antiproton beam)– Correctors: 10 mrad (100 keV antiproton beam)

Aperture – Separation between electrodes: at least 60 mm mechanical aperture– All other components of the assembly (e.g. flanges) should have larger

diameter.

Field homogeneity– “Good field” region: radius 20 mm– Relative change in the good field region: < 10-3

Dimensions– Distances between electrodes and ground: greater than 10 mm– Aperture limiting electrodes (field clamps) to be included to minimize field

leakage and coupling between electrodes.– The overall length and diameter of the assembly should be as small as feasible.

Functional requirements - 2 Electrical

– Conservative values of the nominal design voltages should be chosen (~ 5 kV for the quadrupoles, ~2 kV for the correctors).

– All non-active electrodes must be properly grounded. – Operation in quasi-static mode: no requirement on the switching time.

Powering– The quadrupoles are powered either individually or as a string. The polarity of the

quadrupole is fixed. If necessary, the changes of polarity will be made by modifications in the external circuit. The operating range is from nominal voltage to as low as 100 V.

– The correctors must be powered individually, with variable voltage and polarity. – The voltage stability: 10-4 of the nominal value for the quadrupoles. 10-3 for the correctors.

Alignment tolerances– The changes in the beam orbit due to assembly misalignments must be small compared to

the beam size in the transfer lines.

Vacuum– The assembly must be compatible with the vacuum requirements of the beam lines and

must be compatible with bakeout up to 250 oC.

Interlocks– The power supplies must be interlocked with the vacuum system in each vacuum sector, and

must be short-circuit proof to avoid damage in case of a rapid vacuum loss.

Conceptual design• Standard electrostatic quadrupole

assembly (ZQNA): – two quadrupoles– one horizontal and one vertical corrector– common vacuum chamber– used in all locations, 60 units in total.

• Quadrupoles powered independently with a focusing or defocusing polarity (or with the same polarity if more strength needed).

• H/V correctors powered independently in a bipolar arrangement.

• Electrode assembly mounted on a reference flange, which also serves for rigid attachment of a BPM.

• Assembly fully symmetric around the vertical axis and can be mounted with the fixed flange (BPM) on the left or right.

Main parameters  Quadrupole-1 Correctors Quadrupole-2

Aperture 60 mm 60 mm 60 mm

Nominal strength 6 m-1 10 mrad 6 m-1

Nominal voltage12 kV

(±6 kV wrt ground)

6 kV

(±3 kV wrt ground)

12 kV

(±6 kV wrt ground)

Min electrode-ground

distance10 mm 10 mm 10 mm

Electrode length 100 mm 37+37 mm 100 mm

Polarity F or D H and V F or D

Capacitance 104 pF (tbc)   104 pF (tbc)

Required

Voltage stability10-4 10-3 10-4

HV feedthroughs2-pin SHV-10kV

on DN35CF flange

4-pin SHV-10kV

on DN35CF flange

2-pin SHV-10kV

on DN35CF flange

Length

(flange-to-flange)390 mm

Vac chamber outer dia. 204 mm

Upstream flange DN200CF (fixed)

Downstream flange DN200CF (rotatable)

Mass 30 kg

Performance

• Quadrupoles– Strength Leff = 108 mm, Vmax=±6 kV– Field homogeneity Quad-like shape of aperture plate – Field perturbations from connections OK– Electrical circuit 104 pF (tbc)

• Correctors– Strength Leff = 55 mm, Vmax =±3 kV– Field homogeneity Decoupled and rounded H/V electrodes– Electrical circuit (tbc)

Engineering details

• Vacuum vessel• Electrodes and supporting system• HV connectors• Assembly support• Interfaces

Vacuum vessel

• AISI 316L body, 2 mm wall, 204 mm OD.

• AISI 316LN, DN200 CF flanges (fixed and rotatable).

• Other elements in AISI 304L.• Inside wall NEG coated.

Electrodes

• All materials: AISI 316L, without NEG coating.• All electrodes supported off four rails with

insulator blocks made of alumina 12 mm high.

Electrode support

• Four rails provide precise positioning of the electrodes with respect to the assembly axis. • The rails are connected to the DN200 CF flanges through flange inserts. • On the upstream side (fixed DN200 CF flange), the fixation is rigid. On the downstream side

(rotatable DN200 CF flange), the rails are supported using sliding bolts, which allow thermal expansion of the assembly during bakeout.

HV connectors

• HV feedthroughs with spring loaded pins.• Two/four SHV feedtroughs for

quadrupole/corrector connections on DN35CF flanges.

• Compatible with bakeout to 250 C.• One quote received. Waiting for response of

other (potentially cheaper) provider for the 4-feedthrough flange.

Assembly support

• Four support blocks for connection to the alignment table.

• Clearance between the HV connectors and the alignment table at least 200 mm.

• Appropriate features on the table allow controlled movements of the assembly during thermal expansion (bakeout).

• The alignment table allows horizontal, vertical and longitudinal alignment of the assembly of ±20 mm, and provides longitudinal fixed point counteracting vacuum forces.

Interfaces

1) Beam vacuum system: • two DN200 CF flanges, fixed on the

upstream side (1a), and rotating on the downstream side (1b).

2) Alignment table: • two support blocks upstream side, two

support blocks downstream side.3) HV powering cables: • two 2-pin SHV feedthroughs, • one 4-pin SHV feedthrough.4) Alignment: • two target holders, one on the upstream

side and one on the downstream side.5) Handling tools: • four M10 threads.

1a

2

3

4

1b

5

Production planning

Requested availability– Phase-I installation:

• 10 ZQNA assemblies by June 2015;

– Phase-II installation: • 50 ZQNA assemblies by Dec 2016;

Production planning –EN/MME

12 units21 May 2015

48 units24 Nov 2015

Next steps …

• Complete and approve the Engineering Specification – Aug 2014

• Complete and approve design file – Aug 2014

• Issue orders for component fabrication – Sep 2014

• Prepare Test and Acceptance Procedure – Nov 2014