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QXF instrumentation trace developmentM. Marchevsky, LBNL

• QXF heater trace pattern• Voltage taps layout• Heater delay measurements in LQ• Paschen law and gap between heaters and structure• Bubbles in LQ-style heaters

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QXF: outer layer, mid-plane MTHOMMT = 31.77 mm

a = 10.48 mm (=> 12.11 mm along the cable)r1 = 3 mmL = 15 mm a = 60 deg

m = 3 mmb = 203 mm

29 segments

P/A (straight) = 69 W/cm2 P/A (curved) = 58 W/cm2

Rheater = 5.68 W

Lseg = 230 mmHseg = 31.7 mm

350 V, r=5 10-7 W m, d = 25 mm

Heating station density is 4x less compared to the SQXF.n = 2*109 mm / 12.11 = 18 => hence all strands will be driven normal at once along every 18*Lseg= 4140 mm, or ~0.6 of the full coil length. Hence each strand will be driven normal at least at one spot per full coil length.

(Per 6.70 m)

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QXF: outer layer, pole block MT

HOPMT = 23.74 mm

a = 10.48 mm (=> 12.11 mm along the cable)r1 = 3 mmL = 6 mm a = 60 deg

m = 3 mmb = 207 mm

P/A (straight) = 53 W/cm2 P/A (curved) = 45 W/cm2

Rheater = 6.49 W 29 segments

Lseg = 230.3 mmHseg = 23.9 mm

350 V, r=5*10-7 W m, d = 25 mm

(Per 6.70 m)

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QXF: inner layer, pole MT

Proposal: combine mid-plane and pole block heaters in one, spanning the entire width of the inner layer winding of 45.5 mm

LIMMT =30.75 mm and LIPMT = 9.19 mmEntire inner layer: 45.51 mm

a = 10.48 mm (=> 12.11 mm along the cable)r1 = 3 mmL = 30 mm a = 60 deg

m = 3 mmb = 195 mm Lseg = 230.3 mm

Hseg = 45.3 mm

29 segments

P/A (straight) = 79 W/cm2 P/A (curved) = 66 W/cm2

Rheater = 5.33 W

350 V, r=5*10-7 W m, d = 25 mm

(Per 6.70 m)

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Adiabatic temperature of the heating station

For the highest heating power density, as proposed for the QXF inner layer MT heater (79 W/cm2, 65.7 A of heater current) we obtain temperature rise up to ~340 K!

SS304, d = 25 mm, a = 10.48 mm, T0 = 5.0 KExponential current decay with t = 50 ms is assumed

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QXF voltage tap layout

Compared to the HQ/LQ Vtap layout,no Vtap were placed in the middle of the straight section. Also, Vtap monitoring first mid-plane turn was eliminated. The Vtaps are routed to both ends of the coil, to keep consistent “twisted pair” style connections for every consecutive segment, without making a large loop.

The first CAD version of the trace design is to follow in Dan’s presentation

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LQ delay time vs heater power

OL heaters fired

0 10 20 30 40 50 60 70 800

50

100

150

200

250

START (IL)

Start (OL)

I/Iss (%)

Tim

e (

ms)

78 W/cm2

57 W/cm2

25 W/cm2

40 W/cm2

Data by G. Chlachidze Data by H. Felice

For the outer layer pole block MT the heater power is ~50 W/cm2 at 350 V or ~80 W/cm2 at 450 V.Hence, we are looking to the heater delays of 13 ms (350 V) to 8 ms (450 V) – at 60% SSL

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Paschen law and temperature correction

G. Dakin, "Paschen Curve for Helium,” Electra, vol. 52, pp. 82-86, 1977.

Temperature-dependent correction: P(T) = nkT, or at constant pressure n(T)=P/kT. Thus, 10x temperature reduction would shift the Paschen curve one decade to the left

3 mm gap – 1 atm (RT)

1000 V

3 mm gap at 100 kPa (1 atm) corresponds to 1000 V breakout voltage (RT)However, 6 mm gap would yield ~ 1600 V breakout (less than 2x factor)

~1600 V

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Bubbles in LQ heaters

No bubbles under the heating stations !

Can we introduce narrow linear “slits” in the design of the wide portions of the heater traces?

They will not affect much the trace resistance, but will allow for better impregnation of the heater traces to the coil along the areas that are most prone to bubble formation.