m.apollonio CM18, RAL, 14/6/2007 1

MICE beam diffuser

M. Apollonio , J. Cobb, P. Lau, W. Lau,

J. Tacon, H. Witte, S. Yang - Univ. Oxford

m.apollonio CM18, RAL, 14/6/2007 2

outline A bit of history …

Choice of radius Choice of thickness

Mechanics Control

Conclusion/Plans

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0. Z=-6010 mm for the downstream face of the diffuser. (CR, CM14 Osaka - 2006)

1. radial size R as big as possible

2. thickness limited number of discs to fulfil MICE configurations

3. mechanics & control design still evolving a) new carousel wheel b) motors c) ideas for control (logic)

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radial size

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LEADING IDEA

trying to exploit all the radial space (15 cm) within the envelope

being compatible with mechanical constraints

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7mm 15.5cm

Emi inflation in single layer lead diffuser: 2.8 6.1 mm rad

7mm

emi(after diff)=6 mm rad

Muons selected on the overall channelideal disc

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7mm

7mm

5cm 15.5cm

Emi inflation with a single layerof lead (small radius): 2.8 5.3 mm rad

7mm

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7mm

7mm

5cm 15.5cm

Emi inflation in a staggered lead diffuser: 2.8 6.1 mm rad

7mm 7mm

a more realistic diffuser

fixed annulusmovable disc + support

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emi(

R)/

emi(

R=

30

cm)

R_diffEmittance bias as a function of R_diff (partial inflation)

Pz=209 MeV/c, emi=10mm rad, B=4 T

Pz=148 MeV/c, emi=10mm rad, B=2.9 T

Pz=267 MeV/c, emi=10mm rad, B=4 T

single disc

staggered discs

m.apollonio CM18, RAL, 14/6/2007 1010 mm

Proposal to accommodate many configurations STAGGERED/TAPERED with a fixed external annulus …just a sketch (see Peter/Joseph/Stephanie drawings)

24 t

o 2

7 c

m

30 c

m

trackerdiffuser

envelope

Supports (outer can/disc support): Al

Pb diffuser disc and outer annulus

1.5 to 15.5 mm

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thickness choice

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= 1.4 mm radun-normalized

How many configurations we need? want? …

tD

tDtt

tDt

1122

3211111122

2111122

3/2

2/

20

226.13

ZPX

ZD

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… maybe 5 discs are enough (at least to begin with)Thinner disc: Pb Steel?

MICE note in preparation

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mechanics

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automatic device with 3 main movements & accurate positioning

Carousel (revolving) Discs (+/- 15 deg) Catcher (linear motion through a threaded

cylinder)

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New design

hub

air motors

empty station

diffuser disc on holder

encoder

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Disc 2Disc 1

Dummy Disc

Disc 5

Disc 3

Disc 5

Motor A

Motor B

Motor CP. Lau

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To verify whether the lead is in the bayonet gear or not

To identify which lead is atThe center of the beam

Motor A

P. Lau

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Motor B to drive to turnthe disc holder 15° clockwise& anti-clockwise

Encoder

Encoder Reader

Bayonet Gear;Turn 15° to clockwise to unlock and anti-Clockwise to lock

P. Lau

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This gear is to drive the diffuser catcher forward and backward

Motor CP. Lau

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5 optical sensors to check disc position (4) +disc presence (1)

MICE axis

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4 bit ~Gray code

When this bit is 1 we sense the disc

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2 -switches(check if disc at bottom of TH) 1 optical sensor(check if disc at top of TH)

S1

S2

OS

catc

her

Pb

dis

c +

fra

me

Pb

ext

ern

al a

nn

ulu

s

S. Yang

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OS: carousel and disc

OS

: disc holder

encoder

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0.61 T

0.32 T

0.53 T

B>= 4T

B (T)

Z (m)

R (

m)

motors in the magnetic field can they work ?

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Air Motors

• Must be non- magnetic• Acetal Body, SS shaft, Ceramic bearing.

• The company does it is Dynatork– 10 to 12 weeks deliver time

– The cost is around £1,000 excludes VAT for 3 off

• Working pressure – 100 PSI• The maximum torque is 2.8 Nm• The speed is 200 rpm• No speed control• No positioning control

• What problem we will tackle due to above parameter?

1. How to stop it?

2. Any accuracy concerns?

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For the Carousel

• The total mass is about 70 kg • The moment of inertia is about 5.1 kg m²

• To stop the carousel:-

1. To reduce the speed by introducing the gear box A with gear ratio 200:1, driving teeth ratio 3:1, total reduction is 600:1

2. By use of the binary sensor to read the position of carousel.

3. By using the spring ball and dimple to guide the stop position of the carousel.

4. Use the lock pin to hold the carousel in place before the next motion

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For the 15° disc holder

Drive by the air motor B;

1. To reduce the speed by introducing the gear box B with gear ratio 51:1, teeth driving ratio 7.77 :1, total reduction is 400:1

2. By use of the Heidenhein 4000 series encoder to ensure the very high accuracy of positioning.

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For the diffuser plate transportation

To locate the lead disc;

1. To reduce the speed by introducing the gear box C with gear ratio 3:1 and the teeth driving ratio of 2.7:1, total reduction is 8.1:1

2. Use RS- micro switch to detect the position of the lead disc at the bottom position.

3. Use RS reflective photo sensor to detect the top position of the lead disc.

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Epicyclic Gear Arrangement:

For 1 rotation of shaft L shaft S rotates: ( 1 + NA / NS )

Gear Ratio: (1+42/14) = 4:1 with shaft S as the input.

InputOutput

J. Tacon

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logic & control

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Start: go to Nf

(S1&&S2) off?

OS on?

OS on? Which discis in? Nd

Move C to position Nd

Nd = 0

Extract disc

Move catcher to bottom

Move C to position Nf

Insert disc

Go to dummy station

STOP

Move Catcher to top

STOP !!!ERROR

align disc holder:motor ACW (-15 deg abs)

align disc holder:motor CW (+15 deg abs)

Move catcher to bottom

Go to dummy station

Command: set disc-f for run mode

NB: need to know WHICH disc is in !

Diffuser Control Flow Chart:main cycle

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Diffuser Control Flow Chart:

check discs insertedat the end of this cycle I should have a 5-element vector like (1,1,1,0,1) telling which station is empty. If the number

of empty stations (Ne) is greater than 1 an error is produced which stops the

system

Sense disc

START

GO TO position Ns

Record station (Ns: 0,1)If 0 Ne=Ne+1, Nd=Ns

If 1 NT=NT+1

Ns=1NT=0, Ne=0

Ns>=6

Ns=Ns+1

Go to dummy station

Ne<=1?

STOP !!!ERROR

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Diffuser Control Flow Chart:

move C to position NdRotate CAROUSEL C.W.

(till OS fires Nd)Turn ON motor (+A)

STOP

START

OS firing on mark Nd?

1. STOP motor (A) 2. Push BR-PIN3. Start timer

1. release BR-PIN

t>3 s?

OS reads Nd?

STOP !!!ERROR

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Diffuser Control Flow Chart:Extract Disc

STOP

START

t > 5 s?

1. Pull linear stage OUT = turn motor on (-C)2. Activate TIMER (check extraction time t)

S1 && S2) off?

STOP !!!ERROR OS on?

Turn C-motor offNB motor be stiff/stable

Unlock catcher: turn motor ACW -15deg

Encoder reads -30?

Update DISC position in memory CTRL program

Y

N

Align disc holder(s)turn motor CW +15deg abs

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Diffuser Control Flow Chart:Insert Disc

STOP

START

Encoder +30?

Unlock circular plate:Turn motor CW +15 deg

STOP !!!ERROR

Turn B-motor off (B)Turn on (+C):

• Push linear stage• Activate timer

t > 5 s?

OS off?

Register DISC POSITION in memory for the CTRL PROGRAM

S1 || S2) on?

Turn C-motor off

Y

N

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Integration

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S. Yang

Frascati 2005 CM18 2007

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Quench Studies

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Forces - Structure

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Stresses

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Conclusions

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• “diffuser”: not just a piece of lead across the beam• a staggered/tapered disc+annulus with a clockwork insertion system• thicknesses nearly finalized (assumption on Pz and initial emi.)

• evolved to a rather complicated mechanism • possible flaws/show stoppers need to be found/cured • periodical (weekly) meetings (PL, SY, JT, HW, JC, MA, WL)• external review (?)

• control based on optical sensors and mechanical -switches• design nearly finished (some issues on space) (PL, SY, JT)• gear boxes custom made (JT)

• control logic in progress (MA)

• quench induced forces (HW)

• next step: integration with tracker (SY, WL, …)