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SSR1 Tuner studies(work in progress)

L. Ristori – 29 Nov 2011With slides from I. Gonin, M. Hassan and D. Passarelli

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Overview Reduce the sensitivity to He pressure fluctuations of

the system cavity+vessel+tuner. Allow access for maintenance to motor and piezos

through access port move piezos away from beam pipe

Guarantee an acceptable tuning efficiency (stroke of beam pipe / stroke of motor+piezos, >50%). High rigidity of tuner and/or low rigidity of cavity Mechanical advantage as close to 1:1 as possible (we had

1:5 in the prototype) Guarantee a tuning Range of 200 kHz

Avoid yield Limit the forces required

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Cavity + vessel design was developed for df/dP≈0 The movable beam pipe (left in picture) was left free

(conservative approach).

A Ring couples the cavity end walls with the helium vessel end walls brazed joint will be developed at ANL

• Comsol multiphysicsdf/dp ~ 4.9 Hz/Torr

• Ansys multiphysicsdf/dp ~ -1 Hz/Torr

• Ansys mechanical• df/dp ~ 2.6 Hz/Torr

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The Diameter of the Ring has influence on several aspects.

Of major importance is the robustness of the df/dP value, how stable it is for small variations of the actual cavity+vessel shape.

We can predict (Passarelli) the df/dP value by looking at the deformations of the helium vessel at the connection points with the cavity (here called dRing and dBP).

Ring D=125 mm, df/dP= -0.20 dRing – 0.53 dBP + 23 (Hz/torr) Ring D=140 mm, df/dP= -0.18 dRing – 0.52 dBP + 21 (Hz/torr) Ring D=158 mm, df/dP= -0.05 dRing – 0.57 dBP + 10.5 (Hz/torr) Ring D=192 mm, df/dP = 0.07 dRing – 0.71 dBP + 2.3 (Hz/torr)

Lower coefficients for deformations at the Ring and Beam Pipe give a more stable df/dP

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Study with Ring D = 158 mm Df/dP = 5 Hz/torr (free BPs), 7 Hz/torr (fixed BPs)

df/dP= -0.05 dRing – 0.57 dBP + 10.5 (Hz/torr).

Deformations induced on the cavity+vessel with ring D=158 mm, due to 1 atm He pressure.Beam pipes deformations in the order of few μm.

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If we introduce a tuner similar to the lever prototype, the cavity deforms in an unwanted way.

The G3 vessel is more flexible than the prototype

Interface areas:A: tuning forces on cavityB: motor reaction forcesC: pivoting point reaction forces

When subject to an arbitrary tuning force, the beam pipe area appears to rotate (a) more than translate.Also, the end-wall shape is distorted (b) due to the reactions on the vessel wall (c)

(a)

(b)

(c)

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If we change the leverage layout for the tuner: Translation of Beam Pipe Mechanical advantage reduced to

1:2 (lower is better for piezo stroke requirements)

Reduced stiffness of cavity (increased tuning efficiency)○ Vessel wall and cavity wall move in the

same direction, the reaction forces do not “fight” the tuning forces

Motor+piezos

Actuation pointsPivot point

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2nd option – pivot between motor and beampipe: Similar to prototype Translation of Beam Pipe Freedom of selecting the

optimal mechanical advantage (1:1 – 1:5)

Pivot bridge may be the weak link

M

Actuation points

Pivot point

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Tuner forces: Cavity spring constant

Kc-bare = 25 N/um

Kc-jacketed = 60 N/um

Tuning range 0-200 kHz Tuning stroke:

Tuning forces: E = effort arm / load arm = 1-5

mot

or

Harmonic drive

Scr

ew

nut

arm

Cavity

Fcav

Fnut

le

piez o

piez

o

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Performance (TBC): Motor maximum torque

12.5 N mm Maximum force at drive nut

(12.5 x 100) x 2pi / 1.5 = 52 kN Piezo blocking force

4 kN / piezo

Example Cavity kc = 60 N/um e/l = 2 Fnut = 22 kN / 2 = 11 kN Need 4 piezos of this kind Drive nut at 20% of max force

mot

or

Harmonic drive

Scr

ew

nut

arm

Cavity

Fcav

le

piez o

piez

o

Fnut

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Ahead: Optimal diameter for the Ring

Low df/dp Stability of df/dp to manufacturing variations Low cavity spring constant

Tuning forces on cavity+vessel, do they alter the df/dP? If yes, can we minimize this effect by design?

Tuner design Identify the optimal interface locations Evaluate the required stiffness of the lever arm to guarantee

an acceptable tuning efficiency (beam pipe stroke/ motor+piezo stroke )

Integrate piezo capsules between drive nut and lever arm Allow easy removal/installation of Motor+Piezos block from

cryomodule access port