1. Beam Screens Cooling Update (1st Oktober 2014)
Rob van Weelderen, Gennaro Bozza
Cryogenic Group, Technology Department, CERN

2. Overview Fluka Heat Loads + Explicit Design Margins
Beam-screen cooling cryogenic parameters
Capillary sizing as function of design heat load
Summary beam-screen cooling

3. D1 & IT: Fluka Beam screen heat loads + explicit design margins
1) From F. Cerutti, WP3-meeting 22 May x 1034 cm-2s-1:
“At 5L W on the beam screen of the IT-D1 ” ↓
2) Design with 50 % margin (7.5 x 1034 cm-2s-1) on secondary's 550 W x 1.5 = 825 W on beam screen
3) Provision for 150 W electron cloud
4) Image current load considered marginal
Design for x 1034 cm-2s-1: 975 W at beam-screen

4. Cryogenic beam-screen cooling choices
For high heat loads the optimum functioning has been identified to lie in the 40 K – 60 K temperature range when cooled by helium†
Work with highest practical operating pressure (18 bar – 19 bar), so that helium density is highest, and thus capillaries have smallest possible diameter
4 parallel capillaries are deemed the maximum for practical integration (screen & interconnects)
The Q1 beam-screen capillaries are assumed to be large due to the especially massive tungsten absorbers on this beam-screen: 16 mm OD, 0.8 mm wall thickness
Heat load: 17.1 W/m (corresponding to 975 W over 57 m)
†“Cryogenic Beam Screens for High-Energy Particle Accelerators”, Baglin, V (CERN) ; Lebrun, P (CERN) ; Tavian, L (CERN) ; van Weelderen, R (CERN), 24th International Cryogenic Engineering Conference - International Cryogenic Materials Conference 2012, Fukuoka, Japan, May 2012

6. Summary beam-screen cooling
Design heat load 17.1 W/m x 1034 cm-2s-1 , 975 W total over Q1 to D1)
Q1: 4 x 16 mm OD, 0.8 mm wall thickness cooling capillaries
Q2-D1: 4 x 8.5 MM OD, 0.8 mm wall thickness cooling capillaries
20 bar (absolute) design pressure
18 bar – 19 bar (absolute) operating pressure
40 K -60 K operating temperature
The capillaries extend all the way from Q1 to D1 and traverse all cold masses and interconnects
N.B. 0.8 mm wall thickness needs to be verified with respect to design pressure