1. FDIRC PMTs dimensional tolerance
from Hamamatsu…
“Dimension We measured the window size. The test result was as follows: SERIAL NO.        A [mm]        B [mm] AA0965                51.98         AA0967                51.89         AA0968                51.96         AA0969                51.87         AA0993                51.93         AA1012                51.86         AA1013                52.00         AA1015                51.88         AA1019                52.03         AA1028                51.79         The result showed that the size was smaller than the specs (52.0 mm +/- 0.3 mm). However, we assume that there should be tube to tube and/or lot to lot variation in the size, so we would like to keep the specs of 52.0 mm +/- 0.3 mm. “
Knowing these values for our PMTs will allow to define the smaller PMTs pitch, thus connectors pitch on pcb
2010/05/31 Elba
Massimo Benettoni

2. FDIRC FE boards lodging and cooling
Long FE boards plugged on PMTs and backplane
FE boards plugging as inside crate slots
Power dissipation: up to 1 kW/sector ?
32 FE boards, about 30 W/each ?
+1 pcb concentrator (33° board): W?
+ 1 backplane: W?
FE boards cooling must be uniform and efficient for all of them
concern: convective cooling vs boards pitch: 12 mm
E.g: closed air circuit through heat hexchanger and air filter
Heat exchangers receive deionized cool water from outside the “SOB”
Fans ensure proper air flow
2010/05/31 Elba
Massimo Benettoni

3. FDIRC FE boards lodging and cooling
FE boards plugging as inside crate slots
+1 pcb concentrator (33° board): any dissipation?
+ 1 backplane: any dissipation?
On board fans to perform as much as possible uniform and efficient cooling
Case and panels will make closed air circuit through heat hexchanger and air filter
Heat exchangers receive deionized cool water from outside the “SOB”
Fans must ensure proper air flow
Efficiency of air cooling must be proved
2010/05/31 Elba
Massimo Benettoni

4. FDIRC FE boards lodging and cooling
2010/05/31 Elba
Massimo Benettoni

5. FDIRC Convective heat cooling of PCBs
FE boards surface (two faces): 6dm2
Assuming not all the board surface exchange with same efficiency (due to heat concentrated in some area/components)
let assume 50% area reduction= 3 dm2
Need to dissipate 30W on 3 dm2 .
Let assume Dt (board-air) of 10°C,
Need convective coefficient of a ≈ 100 W/ m3°K
Typical values found (literature) a ≈ 50÷200 W/ m3°K ?
Here geometry does not seems favourable … should we expect low a ?
Air specific heat (volumetric, atm. pressure, 300°K) = kJ/m3°K
Accepting air Dt of 10°C, Flow must be m3/s = 304 m3/h = 5 m3/1’
304m3/h = 84.5 dm3/s
Flow section 1x10x34 cm2 = 340 cm2 = 3.4 dm2
speed = flow/section = 25 dm/s = 2.5 m/s …. Seems low for such high a . .
2010/05/31 Elba
Massimo Benettoni

6. FDIRC Example of heat hexchanger (from Lytron TM)
2010/05/31 Elba
Massimo Benettoni

7. FDIRC Conclusion: some open issues
Magnetic shield: still needed? Which thickness, specs, requirements?
Fbox to be finalized, build prototype, test
Buttons material, tests
Fbox handling and insertion fixture and procedure
Tools and procedure for Fbox+barbox handling
PMTs positioning, C-fiber honeycomb, PMTs optical contact
PMTs replacement procedure
PMT retainement
first iteration to integrate FE boards, PS etc in the 3D model
FE boards fitting, replacement, connection, cooling
2010/05/31 Elba
Massimo Benettoni