QXF instrumentation trace development M. 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

QXF: outer layer, mid-plane MT HOMMT = 31.77 mm 350 V, r=5 10-7 W m, d = 25 mm a = 10.48 mm (=> 12.11 mm along the cable) r1 = 3 mm L = 15 mm a = 60 deg m = 3 mm b = 203 mm P/A (straight) = 69 W/cm2 P/A (curved) = 58 W/cm2 Rheater = 5.68 W 29 segments (Per 6.70 m) 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. Lseg = 230 mm Hseg = 31.7 mm

QXF: outer layer, pole block MT 350 V, r=5*10-7 W m, d = 25 mm HOPMT = 23.74 mm a = 10.48 mm (=> 12.11 mm along the cable) r1 = 3 mm L = 6 mm a = 60 deg m = 3 mm b = 207 mm P/A (straight) = 53 W/cm2 P/A (curved) = 45 W/cm2 Rheater = 6.49 W 29 segments (Per 6.70 m) Lseg = 230.3 mm Hseg = 23.9 mm

QXF: inner layer, pole MT LIMMT =30.75 mm and LIPMT = 9.19 mm Entire inner layer: 45.51 mm 350 V, r=5*10-7 W m, d = 25 mm Proposal: combine mid-plane and pole block heaters in one, spanning the entire width of the inner layer winding of 45.5 mm a = 10.48 mm (=> 12.11 mm along the cable) r1 = 3 mm L = 30 mm a = 60 deg m = 3 mm b = 195 mm 29 segments (Per 6.70 m) P/A (straight) = 79 W/cm2 P/A (curved) = 66 W/cm2 Rheater = 5.33 W Lseg = 230.3 mm Hseg = 45.3 mm

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 K Exponential current decay with t = 50 ms is assumed

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

LQ delay time vs heater power OL heaters fired 40 W/cm2 25 W/cm2 57 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

Paschen law and temperature correction 3 mm gap – 1 atm (RT) ~1600 V 1000 V G. Dakin, "Paschen Curve for Helium,” Electra, vol. 52, pp. 82-86, 1977. 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) 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

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.