fets meeting, 1st november 2006 peter savage the front end test stand collaboration 1 the mechanical...

FETS meeting, 1st November 2006

Peter Savage

1

The Front End Test Stand Collaboration

The mechanical engineering design of the Mk II emittance measurement device.


Peter Savage

2


Mk I Emittance Scanner

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Isometric view of the Mk I emittance scanner that was designed to fit on the ion source test bench at the Rutherford Appleton Laboratory.

Support rods

The ion source test facility vacuum tank

CameraMoving rod

Window

Head

Mounting flange


Peter Savage

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The complete assembly mounted on the stainless steel flange.

Mk I Emittance Scanner


Peter Savage

4


Mk I Emittance Scanner – Head Design

Exploded view of the head assembly

Sliced view of the assembled head

10mm thick copper grid with a 25 x 25 array of 2mm diameter holes on a 3mm pitch.

0.3mm thick tungsten grid with 100 micron diameter holes

Scintillator


Peter Savage

5


Vacuum leak due to damage on sealing faces

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Damage to the inner rod sealing ring, approx. 0.5mm wide and 0.5mm deep.

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The rod has a scratch, approx. 05mm wide, 0.1mm deep, 30mm long.


Peter Savage

6


Mk I was built and used successfully but also has experienced a few problems.

It has been decided that we would benefit from a brand new emittance scanner with improvements made from what we have learned from the MkI. These improvements can be broadly split into three categories:

1) Stiffer support structure – apart from the obvious problems related to movement of the camera when mounted to a weak structure, I believe that the damage shown on the previous slide was due to the moving rod coming into contact with the main flange due to bending of the support structure.

2) Cooled head with a larger grid area – the MkI grid had 625 holes (25 x 25 array) on a 3mm pitch and hence covering 72mm square. This is less than the beam size. Also, damage appeared on the grid due to localised heating by the beam. While beam power is low there is no convection mechanism to cool the grids and so the MkII will have an active cooling system.

3) Improved vacuum seal – before the MkI became damaged the sealing onto the moving rod was working well but an improved vacuum design will be employed for the MkII that will also assist the cooling design.

Mk I Emittance Scanner – Conclusion


Peter Savage

7


The Mechanical Engineering Design of the Mk II emittance measurement

device.


Peter Savage

8


Mk II Emittance Scanner

Light port Handle to be replaced with stepper motor

Bellows mount + window clamp


Peter Savage

9


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Mk II Emittance Scanner – Head design

Tungsten Grid

Glidcop Grid

(aluminium dispersion strengthened copper)

Copper grid cooling channel closing plate

Scintillator Grid

Moving Rod with keyway

Cooling Rods

End plates

KF50 Flange


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With this design there are no removable water joints exposed to vacuum and no moving parts sliding through vacuum seals as in the MkI design.

Mk II Emittance Scanner – vacuum seal

KF50 flange to be welded directly onto stainless steel flange

KF50 flanges joined via bellows similar to those shown here from UHV Design


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11


DO WE NEED COOLING AND IF SO, IN WHAT FORM?


Peter Savage

12


First Simple Model

Model parameters:

Beam Power = 36 W

Material: Copper

Block dimensions: L 100mm x W 100mm x H 100mm

Cooling channel radius 10mm

Ambient Temperature = 25C

Cooling water temperature = 20C, forced convection

Radiation ignored

To investigate whether we need active cooling for the MkII emittance measurement device we can use FEA. First we will consider a copper block, being impacted by beam and being cooled by water.

Beam power

Copper block

Cooling water


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First Simple Model

Model parameters:

Beam Power = 36 W

Material: Copper

Block dimensions: L 100mm x W 100mm x H 100mm

Cooling channel radius 10mm

Ambient Temperature = 25C

Cooling water temperature = 20C, forced convection

Radiation ignored

n1

n2

n3

n4

e1

e2

e3

The model as shown in figure 1 can be shown in it’s simplest form as in figure 2. This can be modelled using simple link elements and can also be solved using matrices and hence acts as a verification model.

The simple 1D model from figure 2 was then expanded to the 2D form as shown in figure 3 to better illustrate the effect of the beam power and the cooling.

Figure 1. A simple model with symmetry

Figure 2. A 1D model with link elements.

Figure 2. A 2D model using PLANE55 elements


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Calculating convection coefficient for cooling


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Calculating convection coefficient for cooling


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Nodal temperatures

After 1 minute:

Tmax = 24.8°C

Tmin = 23.6°C

Nodal temperatures

After 10 minutes:

Tmax = 22.7°C

Tmin = 21.8°C

Nodal temperatures

After 30 hours:

Tmax = Tmin = 1198°C

First Simple Model – cooled, radiation ignored

For a beam power of 36W, cooling water temperature of 20°C, initial temperatures of 25°C throughout (and convection coefficient of 3000W/m2.K). After about 6 minutes the block cooling reaches a thermal equilibrium with the beam power. With cooling switched off, after about 30 hours the OFC block will exceed the melting temperature of 1082°C.

Water cooled @ 20°C Water cooled @ 20°C No cooling

Temperature change with time for nodes along the right hand edge (representing the centre of the 2D model).


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Emittance Measurement Device – 36W for one hour

Conclusion: A cooled rod or grid allows a thermal equilibrium to be reached. It is recommended that for either cooled solution a time of approx 2000 seconds / 30 minutes is

allowed to elapse before taking data to let the grid stabilise.

No cooling Rod water cooling alone Grid water cooling alone

Tmax = 60.0°C

Tmin = 43.7°C

Tmax = 37.0°C

Tmin = 25.0°C

Tmax = 22.2°C

Tmin = 20.2°C


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Displacement due to heating - cooled grid

Maximum displacement

in X direction = 0.018mm

Maximum displacement

in Y direction = 0.041mm


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THE RESULTS FROM THE THERMAL CALCULATIONS HAVE PROMPTED THE

DEVELOPMENT OF A NEW DESIGN


Peter Savage

20


Simplified cooling scheme

Mk II Emittance Scanner – revised

Improved camera mount

Rod mounts optimised for strength versus size to allow for motor to be mounted close to the main flange

Tip / tilt stage

Translation stage

The combination of the tip / tilt stage with translation stages for X and Z and a custom translation adjustment for Y creates a system that is adjustable for all six degrees of freedom.

Z

Y

X


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21


UHV Design

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The search for a long travel edge welded vacuum bellows led me to this company called UHV design.


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22


LSML64/35 700SD Linear Shift Mechanism

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Side and end elevations of the LSML64 from UHV Design


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23


Quote From UHV Design

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UHV design will also be quoting for cooling using their support tube and for electrical feed-throughs for strain gauges.

Item

Qty Part Number Description Price Each £

A 1 LSML64/35-700-SD

Long travel linear shift mechanism mounted on a CF64 (4-1/2" OD CF) flange with a CF35 (2-3/4” OD CF) travelling flange. Both flange have metric tapped boltholes. 700mm stroke. 38mm bore bellows (this is reduced with the support tube fitted). Price includes a bellows support tube, demountable bellows assembly, a side-mounted DC motor and timing belt cover. Price also includes pre-wired bakeable limit switches.

£7,573.00

B 1 SADC Bench-mounted DC motor controller for Item A.

£404.00

C 1 EWB-3044-1 316L bellows assembly with CF35 (2-3/4” OD CF) flanges. 700mm stroke. 39mm ID x 59mm OD. Bellows length = 154.0-854.0mm plus flanges and tubes. 10,000 cycle lifetime.

£1,628.00


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24


New design with LSML

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The new design showing just the bellows from the LSML.


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Conclusions:

•Purchasing the LSML from UHV Design will reduce the manufacturing effort and will provide a proven working system that will reduce ‘fine tuning’ time dramatically.

•The cost of the LSML purchase may not prove to be significantly less than the cost to manufacture my design.

•The remaining design work and manufacture for the main flange, the camera mount and grid + grid mount can proceed in parallel with the manufacture of the LSML.

fets meeting, 1st november 2006 peter savage the front end test stand collaboration 1 the mechanical...

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