S. Stanic 25-Jul-2000 Estimation of the HOM Heating of SVD 1.2 Beam-pipe from the measured temperature raise On 5-Jul-2000 KEK-B was operating in a single beam mode and raising beam current by 100mA for each HER and LER beam. For HER (positron) beam Fill Pattern was 8/159/4 (1), nbunch=1145 and for LER (electron) it was 8/159/4, nbunch=1146, bunch revolution frequency 100 kHz. HOM calculation --------------- Longitudinal loss factor for SVD 1.2 structure 0.37 V/pC and fraction of trapped HOM that goes into heat was found to be less that 0.05 (see Belle note 341), so the upper limit on heating power is calculated as P_Heat = 0.05 * P_HOM = 0.05 * k_l * I**2 / f_b / n_b For the above beam conditions, P_Heat in the central (Be) region assuming uniform heat generation is thus: I_beam(mA) P_Heat(W) ------------------------- 100 0.5 200 2. 300 4.6 400 8.3 450 10.5 Temperature measurements ------------------------ Temperature data were thus taken for 100, 200, 300, 400 and 450mA for each HER and LER while Belle took background data and stored them in runs 2474-2478, 2480-2484. Temperature measurements were logged at about every 1-2 seconds and stored in the monitor ntuple. Positions of Temperature sensors: No. Location ----------------------------------------------- 42 z=195mm from BWD flange 41 Be centre 33 Be centre 34 z=285mm from FWD flange (closest to Be part) Results: Temperature at Be centre seems to be raising linearly with current, while at both ends of Be where water cooling is available it seems to be reasonably flat. Sensor no. Rise (K/A) for HER Rise (K/A) for LER ---------------------------------------------------------- 33 0.81 0.94 41 0.65 0.73 34 -0.08 0 42 0.14 0.15 No. T(I=0) HER T(I=0) LER ---------------------------------- 33 14.87 14.75 41 14.35 14.22 34 12.5 12.4 42 20.78 20.70 (I don't know why T is so high) Sensor 42 is clearly too far from Be part and clearly influenced by other sources of heating, and therefore not of much use. Heat generated in the Be section as a function of I_beam was thus estimated from the relative increase of the temperature difference of the two points, 33 and 34. I(mA) (T(33)-T(34))_I - (T(33)-T(34))_I=0 (deg. C) ---------------------------------------------------- 100 0 200 0.082 300 0.073 400 0.256 450 0.349 Other experimental conditions (mean values) ------------------------------------------- P(He)_In=97kPa P(He)_Out=34kPa He flow rate=22.7 m3/h Room temperature=26.18 C Temp. around Belle structure=29.35 C Chiller temperature=12.75 C T1 ========================== T_He(in) He He He He He He He He He T_He(out) T2 ========================== - - - - - - - - - - - - - P=? ========================== He He He He He He He He He ========================== 34 33 Analysis -------- The above temperature raise was simulated by a model of double wall Be pipe with He cooling and longitudinaly uniformly distributed heat generation as used by Asano and Zhang. Result of the simulation is that the heating power of 31W contributes to 1K relative temp. rise between sensors 33 and 34., i.e. (T(33)-T(34))_I - (T(33)-T(34))_I=0 (C) P_sim (W) ---------------------------------------------------- 0 0 0.082 2.5 0.073 2.2 (something strange) 0.256 7.8 0.349 10.6 The heating power that reproduces measured temperature raise between the centre and end of the Be pipe was thus found to be in good agreement with the value obtained from the HOM heating analysis.