Reviewers report of the LHCb C0 2 cooling EDR EDR date: 3 rd of December January

Remarks & Questions on Velo evaporator concept Remarks: 1.It has been discussed during the meeting that all the detector has to be 186 bars (When using 130 bar burst disks. 1.43x130=186) 2.Please remember that the guarantee dew point of the dry air network 3.Please specify the grade of CO 2 purity you request because it’s one of the main point to define the redundancy logic (Alternatively: It is highly recommended to construct the system such that it can successfully operate on standard CO 2, available in the CERN store.) 4.The micro-channels have to be tested under the worst conditions: high pressure / fast temperature drop / water hammer (increase the pressure without a ramp) 5.You have to do some tests to understand the full pressure drop of the detector cooling loop not only the one of the micro-channels (valves / pipe in / micro- channels / pipe out / non-return valve) 2

Remarks: 6.Concerning the safety, you are doing several tests to know the pressure in the secondary vacuum if one of the microchannel fails, means 3.57ml. It’s important to do this test taking into account the reaction time of the pneumatic valves following the length of the pneumatic pipe between the electro valve and the actuator. There is experience that non-return valves tend to leak. Important to verify this since this can raise the pressure on the membrane. 7.You have to propose a detector test campaign because it’s not clear. 8.Please specify the maximum downtime you can accept (means no cooling and no circulation) 9.Please mention the temp ramp down & UP (e.g. 1°/min) Remarks & Questions on Velo evaporator concept 3

Remarks: 10.Without heat load, the flow is 1.5 times bigger than with the heat load. The design should take the pressure drop due to two-phase flow into account. 11.It is important to make a schematic of the complete cooling system including detector and plant. 4

Remarks & Questions on Velo evaporator concept Questions: 1.You don’t know how you will test the full detector or at least half of this one How are you sure about the internal distribution of the CO 2 through the different loop? How do you think you will control the boiling point in the micro-channels? 2.Why do you want to put a filter in the tertiary vacuum? (Could it not be in the manifold box on the cavern wall?) 5

Remarks: 1.Please specify the maximum downtime you can accept (means no cooling and no circulation). 2.Please mention the temperature ramp down & up (e.g. 1°/min). 3.A global test has to be done at the end of the assembly. 4.You have to provide a scheme of the test bench in surface to be sure about the design of the Lucasz plant (size of the accumulator) Remarks & Questions on UT evaporator concept 6

Questions: 1.Do you think it’s necessary to test the stave under thermal shock? 2.Is the 2bar pressure drop over the capillary enough to assure correct flow distribution in all cases? Remarks & Questions on UT evaporator concept 7

Remarks: 1.On the current P&ID, there is no way to pressurize the detector from the Lucasz plant to do a leak check for example. 2.On the 3D it seems there is pipe above the motor of the pump, think about the maintenance 3.I will not remove the ‘’service components”. 4.If LHCb has a low temperature chiller maybe consider to use this chiller and you will save 11kCHF. 5.Experience in CMS has shown that the concept of including a cold box in the cooling plant has numerous well appreciated advantages. It would be good if this can also be implemented in the VELO plant design. 6.The design of the frame looks very light considering that LEWA pumps generate vibrations. Frames should be rather rigid to avoid resonance. 7.The design does not look like it is optimised. More compact seems possible. Remarks & Questions on Lucasz concept 8

Remarks: 8.During LS2, the CMS P5 surface plant “LUCASZ” will not be available for testing of LHCb detectors. 9.The backup chiller strategy needs further study. An integrated approach between VELO and UT seems to give important advantages. 10.For VELO as well as for UT, it is important to work out the strategy for redundancy, for the plant as well as for the detector. A schematic making this clear should be made, after the strategy is worked out. 11.Based upon flow distribution and redundancy, the trade off between a constant flow and a constant pressure system should be studied. 12.A good trade-off study between safety valves and burst disks should be performed. Safety valves often leak, burst disks require higher system pressures. 9

Questions: 1.Is there compressed air in the assembly area? Remarks & Questions on Lucasz concept 10

Remarks: 1.Concerning a common chiller for UT/Velo & SciFi, it will be decided after formal numbers about the operation temperature and the power of SciFi Think about a P&ID: direct expansion or mono-phase brine … 2.Concerning the proposal to have 1 full power chiller and one with limited power, this means that you can easily loose one day a data due to the time of the repair. 3.I don't see in the P&ID the possibility to do the vacuum in the lines after the pneumatic valves of the junction box I think it could be useful. 4.Please remember that the guarantee dew point of the dry air network Remarks & Questions on cooling plant & transfer lines concept 11

Questions: 1.Almost all the sensors are doubled, is it really necessary? I can understand it for the Temperature Transmitter (TT), but for the Pressure Transmitter (PT)? Is one PLC with redundant sensors safe? 2.In case of interconnexion is there is any risk to get water hammer phenomena? 3.If one chiller fails and the plants are cold, how do you think to proceed? If the heat exchanger is cold, there is the risk of condensation inside. 4.Are you sure that the regulation valve AV1A/C/1020 will work with 100m of cable and in the magnetic field? 5.If one filter is clogged we need to stop the system for a while (~1day). Is it a problem during data taking if you have to modify the temperature of the detector to comply with the other system? Remarks & Questions on cooling plant & transfer lines concept 12

Questions: 6.The two plants will be designed for 7kW cooling power (for the case of failure or maintenance), which means we will permanently use the heat exchanger of the plants with something between 30 and 50% of capacity, are you sure there is no risk of oil accumulations due to low speed in these ones? Remarks & Questions on cooling plant & transfer lines concept 13

Others remarks & questions Remarks & questions: 1.For me a lot of things are not completely defined and have to be cleared ASAP: Can we mix CO 2 in the both plants Is the working temperature always the same or not (important for the interconnexion) If 1 plant fails, can we continue the data taking … 2.A kind of safety file / operational description has to be write to understand the user requirements. 14