Agenda

Minutes

Present: Hovanes, Pavel, Vitaly, Tim, Moskov, Eugene, Igor, Sashi, Beni, Richard, Mikhail, Marshall.

Pavel continues studying the option of 20% radiator in FLUKA. The W-plug length was 14cm and Be-target length was 40cm. The cylindrical Be-target in this FLUKA model is embedded in a copper block that is supposed to cool the Be-target and also absorb beam power passing around the Be-target.

Pavel also included the tungsten material of KLF Active Collimator ~50cm in front of the KPT assembly.

The γ-beam width in the cave with 20% radiator is considerable wider than with 10% radiator. As the AC diameter is only 6cm wide, there will be large overlap between the beam envelope and AC material leading to power deposition in AC and elevated radiation in the cave.

According to FLUKA, each tungsten wedge absorbs about 90W from the photon beam. Thus Pavel's estimate for the total power deposited in AC is about 400W.

Richard noted that the Boron Nitride cup holding the tungsten wedges is a decent heat conductor and that the wedges can be cooled through the Boron Nitride cups. He will be in contact with Pavel regarding cooling requirements for KLF AC.

Radiation dose rate from neutrons doubled compare to that without AC. γ-dose-rates did not change so much.

Tim commented that Active Collimator is attached to the KPT assembly and the long distance between KPT and AC may cause elevated radiation rates.

Moskov asked for a summary of the presentation. Pavel answer was that this is work in progress and that he will have more updates at the future meetings.

Hovanes showed his thermal analysis of the tungsten plug and Be-target for the 20% radiator scenario.

First, Hovanes used power deposition map for 10% radiator evaluated by Vitaly a few years ago in FLUKA, and multiplied the power in that map by a factor of x2. The resulting temperature in the tungsten plug estimate for such power deposition distribution was pretty high, T_max=350 ⁰C.

Then Hovanes used the new power deposition map from Pavel's FLUKA simulations for 20% radiator. He considered a single block containing Be-target, W-plug, and copper around the Be-target as a single body cooled from the four sides by water. The temperature in the plug and the Be-target was about the same as for 10% radiator.

Eugene would like to see the same simulation with 10% radiator as he thinks it is suspicious that the temperature of the tungsten plug did not change. Hovanes pointed out that we have copper block around the Be-target with 20% radiator option that is not there for current KPT engineering design for 10% radiator. This copper block takes away 2.8 KW power from reaching the tungsten plug.

Hovanes thinks that from thermal analysis point of view, 20% radiator option is feasible. But cooling inside of KPT assembly would need to be substantially modified as there will a lot of power deposition added to the whole KPT assembly.

Hovanes also showed three distinct options for KPT assembly designs that can be currently pursued by KLF. A decision needs to be made by the KLF collaboration leadership which way to go, but the decision needs to be made very soon as delays will negatively impact KLF construction schedule as well as the NPD scheduling process.

Richard continued his studies of the detector rates in KLF using his GEANT4 model .

Richard announced that some of the results shown at the previous meetings were not correct. He found that some jobs crashed that made the results shown at the meeting from the wall shielding incorrect. The slides posted on the meeting page show the corrected plots, not the ones shown at the meeting. The wall and the shielded pipe results provide very similar results. The improvement in the CDC by either shielding scheme is less than factor of x5. The slides posted on the previous meeting page show the corrected results.

Richard tried to optimize the shielding of the detectors by changing the aperture of the beam-pipe after the collimator cave between 4cm and 6cm. He considered two options of shielding: the one with thick iron pipe where he varies the inner diameter of the pipe; and the other one with a lead shielding wall in front of the target cart where he varies a diameter of lead collimator. In both options, W-plug was fixed to 14cm.

The results from both option look similar so far. The CDC rates are reduced on average by a factor of x3 (correspond to about 5cm aperture of the pipe). Richard thinks that the shield wall may allow more kaons through.

Richard needs to simulate detector rates without the extra shielding with W-plug thickness fixed to 14cm to be able to make comparisons. Hovanes also suggested to have the count number in 64ns burst to be able to compare to GlueX-II.

Pavel pointed out that reducing beam aperture from 6cm to 4cm will reduce kaon rates by another factor of x2.

Next meeting will be on December 12th. Hovanes may be unable to chair it as he will be on vacation.