DEVELOPMENT OF SSR2 FOCUSING LENSES FOR PIP-II (Design ...€¦ · February 17, 2020 IIFC Magnet...

DEVELOPMENT OF SSR2 FOCUSING LENSES FOR PIP-II (Design Studies for Conduction Cooled Magnet)

Electromagnetic Application Section

Electromagnetic Applications & Instrumentation Division

Team members: Kumud Singh, Janvin Itteera, Mahima, R R Singh , Rajesh Chimurkar, Rajesh Jalan & Sanjay

Malhotra

February 17, 2020 IIFC Magnet meeting presentation - Kumud Singh | SSR2 lenses For PIP-II

Vacuum pumps

Cryostat housing magnet

Electronics rack

Power diode connected in shunt with magnet

• Functional requirement specification

• Electromagnetic design

• Bucking coil optimization

• Corrector coil design

• Static thermal analysis

• Operating design margin

• Fringe field at cavity surface

• Nominal Operating Design Margin

• Thermal analysis

• Quench design

• Conclusion & Summary

Outline


Functional Requirement Specifications (FRS)

Parameters SSR1 Earlier

Specifications

SSR2 Earlier

specifications

SSR1/SSR2 New

specification

Focusing Strength 4.0 T2m 5.0 T2m 4.5 T2m

Bending strength of Dipole correctors 2.5 mT-m 5 mT-m 5 mT-m

Beam pipe aperture 30mm 40 mm 40 mm

Uncertainty in the location of magnetic

axis w.r.t Reference points (Transverse

and angular alignment)

<0.1 mm RMS

<0.5mrad RMS

<0.1mm RMS

<0.5 mrad RMS

<0.1mm RMS

<0.5 mrad RMS

Effective length of solenoid (FWHM) Insertion length of

Max 160mm

<15 cm Insertion length of

Max 180mm

Active magnetic shielding requirements 0.5Q0 criterion

-

-

Maximum current in the solenoid 100A 100A 100A

Maximum current in the dipole

correctors

50A 50A 50 A


Electromagnetic Design

Sr. no Parameter Value Unit

1. Length of solenoid coils in the lens 120 mm

2. Main coil inner radius 28.75 mm

3. Main coil outer radius 62.5 mm

4. Strand diameter (bare) 0.4 mm

5. Winding fill factor 0.65

6. Number of turns in the main coil ~13500

Sr. no Parameter Value Unit

1. Length of Bucking Coils 55 mm

2. Bucking coil inner radius 85 mm

3. Bucking Coil outer radius 95 mm

4. Strand diameter 0.4 mm

5. Bucking Coil Z location* 32.5 mm

6. Winding fill factor 0.65

7. Number of turns in the Bucking coil ~1833

Objective function :

𝐵𝑧2 . 𝑑𝑧 ≥ 5 T2m

Minimize 𝐵. 𝑑𝑙 𝑟=0.3

𝑟=0 at z= 0.5m

Constraints: 𝐵𝑧∗𝑑𝑧

𝐵0 ≤ 150 cm

I exc < 100A

Optimization Parameters:

Nmain, OR main, IR main , OR main

NBC, L BC , Z center-BC


Electromagnetic Design… continued

B field vs axial distance plot


Electromagnetic design … continued

FWHM = 134 mm

Zonal plot of Magnetic field at the magnet center (field homogeneity 1.4%)

B field plot and B2 Plot along the axial length (Focusing strength of 4.736 T2m) and FWHM of 134cm


Dipole corrector design

Zonal field plot of dipole field in the magnet aperture


Dipole Corrector design

Magnetic Field (Bx or By) plot in the lens aperture

at various radial locations when corrector coils

are connected as skew quadrupole

Bx field plot vs transverse distance in magnet

aperture (Gradient = 2.59T/m)


Electronics rack


2D sketch of magnet assembly

Note : Not to scale


Electronics rack


Magnet Model & 2D Drawing


Bucking coil optimization

B field vs axial distance plot for different cases of Bucking coil dimensions


Vacuum pumps Electronics rack


Superconducting Wire strand material properties

• All conduction cooled magnets are proposed to be wound using round 0.4 bare diameter /0.44

mm insulated strand (NbTi/ copper matrix 1:1.3 Sc:Cu Ratio) from LUVATA (OK636).

𝐵𝐶𝑇 = 𝐵𝑐0 1 −𝑇

𝑇𝑐0

2

The ratio of the maximum current density in the superconductor at any magnetic field and

temperature to that at B = 5 T and T = 4.2 K can be found using the expression given below:

Jc(B,T) / Jc(5 T, 4.2 K)= C0/B∙bα∙(1-b)β∙(1-tn)γ

Where, C0 = 28.4 T, α = 0.80, β = 0.89, and γ = 1.87.

Bare Wire

Dia

Filament

Diameter

Cu/Sc Ratio Filament

twist pitch

RRR Ic @ 4 T ,

4.2K

Ic @ 5 T

, 4.2K

Ic @ 7 T ,

4.2K

Ic @ 8 T ,

4.2K

0.4mm 10.5 μm 1.3:1 50-100mm Min 60 180 A 140A 80A 55A




Nominal Operating Design Margin

3K


Fringe field on cavity surface

Φtr= 2μ0Φ0

(Rs∙ ξ02)

* f∙V

(ΛQ0)

*(1−η)

η

μ0=4π∙10-7H/m ; Φ0=2∙10-15Wb

ξ0=3.9∙10-8 m is the coherent length in Nb, f is

the frequency of the cavity,

Rs is the surface resistance of Nb at this

frequency,

V is the volume of the cavity,

Λ = Magnetic energy density at the location of the quenchAverage energy density in the cavity

Completely defined by the properties

of superconducting material Cavity Specific

Acceptable degree of

degradation η with

allowed amount of the

trapped flux.

Surface integral / line integral at the maximum

magnetic energy density location needs to be

minimized during the design of bucking coil

Placement of a focusing lens inside the SSR cryomodule


Fringe field on cavity surface for two probable choices of Bucking coil


Fringe field on cavity surface for two probable choices of Bucking coil

So optimized design

is chosen to be BC

IR = 85mm

OR=95mm

Length = 55mm

Z center = 32.5mm


Thermal design (Static thermal simulations)

3D model for thermal simulation

Half model with highlighted heat flux boundary condition

Heat Sink – Fixed temp 2.15K

Heat Flux = 𝟏𝑾

(𝟐∗𝝅∗𝒓∗𝒉)




Static Thermal Analysis (no EDM cut in beam pipe)

Case – a (SS Bobbin 0.2mm plating thickness)

1W heat on beam pipe

Heat sink face anchored to 2K




Static Thermal Analysis … continued (with EDM cut to isolate beam load)

Case – b (SS –bobbin 0.2mm plating thickness) EDM cut on beam pipe




Static Thermal Analysis … peak temperature in coils for case 2

Main coil Dipole Corrector coil Bucking coil


Quench Design

+ PS -

V Tap1 V Tap2 V Tap3 V Tap4

Quench Protection by passive

diodes

Differential Voltage between

Main coil 1 and main coil 2 can

be sensed to detect Quench

To reduce noise, resistor can be

used in series

Two voltage taps can be used

per pair of Corrector coil also

BC coil1 MC coil1 MC coil2 BC coil1




Quench Design (Quench initiated in Main coil)

At t = 0s At t = 0.01s At t = 0.1s At t = 0.4s

At t = 5s

At t = 20s

Flux initiated by

1W of heat

deposition at peak

B field location


Peak temperature and voltage in coil

Peak Voltage Current Resistance


B field level at Current lead location

Peak field of 0.04T at 150mm

away from magnet axis




Conclusions and summary

• Magnet design has been completed and the design values meet the

requirements stated in FRS

• Quench initiated in Bucking coils results to be compiled . (Transient) Quench

simulations are pending. This is to include heating due to eddy currents.

• Current lead engineering design to be included in FDR.

• Manufacturing drawings initiated.

• BPM interface and Cryomodule interface required to complete manufacturing

drawings.

Thank You for your kind attention


DEVELOPMENT OF SSR2 FOCUSING LENSES FOR PIP-II (Design ...€¦ · February 17, 2020 IIFC Magnet...

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Transcript of DEVELOPMENT OF SSR2 FOCUSING LENSES FOR PIP-II (Design ...€¦ · February 17, 2020 IIFC Magnet...