Dear Vladimir:

Thank you very much for your reply.  

There is one feature of SoLID that is different from other facilities: The SoLID spectrometer will be used/shared by two sets of experiments that require very different configuration of the EC. THis is described in Table 1 and Figure 7 of the writeup we sent you last time. THe two configurations are called PVDIS and SIDIS. In Figure 7, the PVDIS configuration contains the blue and green areas of (a), while the SIDIS configuration contains the red and blue areas of (a) as well as (b).  So the EC has to be designed in a way where swapping between PVDIS and SIDIS can be done at relatively short time and low cost.  

In the following please find our answers to your questions. I have also numbered your questions for easy references.

I. Preshower:
Ia) Now, the preshower are placed inside calorimeter module. In this version exist significant disadvantages: complicated construction of calorimeter module, new untested design for calorimeter module and cost increase. Of course it's possible to produce but exactly will need a test few prototype. In slide 7, page 2 (your attached file with EC design) shown calorimeter with preshower. Between preshower and Shashlyk should be gap 30 or 40mm for bend preshower fiber.

- Answer: We can certainly reserve a gap of 30-40mm between preshower and shower parts. Building the preshower inside the module is really our preferred option, since during swapping we will only need to rearrange the modules.  I understand building the preshower inside the module requires some R&D from the IHEP side, but in the long run the extra cost of R&D and making individual modules might be offset by lower cost during swapping between experiments.

Ib) Also length of light guide, 100mm in slide, can be reduce on 30-40mm, if shower WLS fibers collect in four optical connectors.  In this case 100x100mm**2 module and 50x50mm**2 module will uses the same connectors and the same equipments can be use for assemble.

- Answer: Both are possible. We are talking to a local company who claimed they can make plastic "plates" with a lateral size of about 10x10cm and with 100 holes to connect the WLS and the clear fibers. The quote is about $175/module. In fact, if IHEP can make similar connecting plates with lower price, it will probably be our preferred option due to reduced shipping cost. Can IHEP make these fiber connectors?

Ic) Would you examine to build two independent detectors, preshower and calorimeter with independent support structure, like in LHCb?

Id) In this case, lead converter can build from few large pieces, that will simple and cheap. All read out fibers can be easy send to the side of detector, also LHCb expirience can be use.

Ie) In this case, lead converter can build from few large pieces, that will simple and cheap. All read out fibers can be easy send to the side of detector, also LHCb expirience can be use.

- Answer:  As mentioned above, we really prefer the individual module design. Making two independent detectors will make the swapping much more difficult.  For the lead plate we can possibly use 3 indepent lead plates of "ring-shapes", one for PVDIS and two for SIDIS, but we still need to swap the scintillator behind and the fibers. The extra cost and manpower need during this swapping period is what we really want to avoid. 

If) Also in LHCb preshower detector consist of two layers of scintillator pads separeted by lead plate. First layer of scintillator pads placed in front of lead convertor use for photons/electrons separation. Do you need photons/electrons separation?

- Answer: the SoLID has a tracking device GEM (Gas-Electron-Multiplier) in front of EC. The tracking will be sufficient to reject photons. We want to avoid scintillator in front of the lead because of the high radiation damage. 

If) Can you reduce a thickness scintillator in preshower from 20mm to 12mm or 10mm? The fact is that 20mm scitillator with size 10x10cm**2 can't be produce by the injection molded technique in IHEP. I discussed this question with Sergey Chernichenko, he is head of scintillators subdivision. But it's possible for 12mm and exactly for 10mm thickness. As I understand for preshower will be need 25-30 photoelectrons for MIP, I think that this light yield can be achieved with 10mm scintillator.

-Answer: We started from 15mm and decided to use 20mm to allow extra security. 10 or 12mm would be too thin. Would it be possible to make two 10-mm scintillators and just put them back to back? The WLS fibers can be sandwiched in between. The cost per module to use two scintillators seems to be moderate compared to the cost of the shashlyk.

- On a separate note, if we do integrate the preshwer inside the module, the mold for shashlyk will need a small dip on the side to allow the Preshower fiber to go out. Preshower fiber has to be wrapped for light isolation. And we will look into possible fiber casing for the light isolation.

Price estimation for preshower scintillator with size 100x100mm**2 and thickness 10mm (100g weight):

Version A (production scintillators using the process of styrene polymerization in blocks): production scitillator pad near 8-10USD/pc and machining grooves near 20-25USD; in total near 30-35USD per scintillator without assemble.

Version B (production of molded scintillators): price of mold for scintillator with groove near 30kUSD or near 17USD/pc and production scintillator near 3-4USD; in total near 20USD per scintillator without assemble.

Version A have few advantages: light yield of scintillator is higher on 10-20% and scintillator more transparent. Also for version B groove in scintillator will be slightly tapered, if on depth the width of groove will be 1mm then width on surface will be 1.1 or 1.2mm. It's disadvantage of version B, as during inserting of fiber in the groove will need additional tool for keeping fiber inside scintillator.

The two type of scintillators can be produced in IHEP and also we can order similar scintillators in outside firms.

-Answer: At the moment we don't have a preference between version A or B. However, would version A allow more flexibility for inserting the fibers?  For example if we design to make the groove deeper towards the side, to allow some bending of the fiber and therefore less bending once the fiber goes out of the scintillator, then would the mold method be easier than machining?


II. Support modules:
First electromagnetic calorimeter in COMPASS has similar size 3x4 m**2 and total weight of calorimeter modules is 24t. The mechanical platform, chariot and light isolated cassette was designed and produced in Protvino workshop. ECAL1 calorimeter can move in three direction along vertical and horizontal and also along beam axes.
I send you two photos with ECAL1 cassette and chariot. I have all working drawings and I can send you if it's need.

-Answer: So far we have not put much thought into the supporting structure yet and it will be one of our major to-do item for the near future. The support will have to come from the floor, although from the "nose" (center of the ring-shape) will not be out of the question. What I see the main difference between our EC and COMPASS is still on the experimental swapping. The supporting structure must allow quick re-arrangement of all green blocks of Fig.7a into red blocks of Fig.7a and blue blocks of Fig.7b, and vice versa. So supporting from the floor/bottom might not be preferred, since in that case to remove green blocks from the bottom one needs to remove all blocks above them, which means the whole EC has to be dis-assembled. 

- If you have any suggestions for how to design the support structure, we would like to hear them. 

III. Calorimeter module.
 I will consider design and cost estimate for Shower 18X0  Shashyk, as shown in your slide 7, page 2. Some assumption: 
1) we will build a straight Shashlyk, due to large impact angles. It's correct? 

- Answer: yes, if "straight" means the WLS fibers in the shashlyk are along straight lines.

2) the cost of preshower will not included; 

3) the all materials and press mold will be produced and buys in Russia and/or IHEP. Of course WLS fibers, optical connectors and also diamond cutter and mill will be better to buy in USA or Europe.

-Answer: We will buy WLS fibers and have them shipped to you. For optical connectors, as mentioned above, we have quotes from a local company which is about $175/module for one plate to connect 100 WLS fibers with 100 clear fibers. The same company will look into making the connectors between the clear fibers and the PMTs (We will use 28mm-diameter PMTs). but if IHEP has relevant expertise, that would be an option too.  We have not looked into diamond cutters but will do so.

- On a different note, does IHEP have any expertise in fiber fusing between WLS and clear fibers?  That would be option for the Preshower.

So I don't add: preshower price, optical connectors, WLS fibers and mirrors on fibers, overheads cost in IHEP, transportation cost, assemble and production tools.

- Answer/question: Can you explain what "mirrors on fibers" refer to?

- Answer/question: What is the overhead cost ratio at IHEP?

Looking forward to your further discussions.

Merry X'mas etc.

Xiaochao