# Presentation: 582776

## A strawman design of a containerized RPC-based detector

- Low Z tracking calorimeter

- Issues:
-  absorber material (_Particle board?_ OSB? Other? )
- longitudinal sampling (__X0)?
- What is the detector technology (_RPC?_  Drift tubes?)
- Transverse segmentation 2? _3?_ 4? 5? cm
- Monolithic? Modular? _Containerized?_ detector
-  Distributed electronics? _Signal processing at the outer periphery?_

## The fundamental issue: low cost detector

- Use standard materials whenever possible:
- Float glass
- Particle board
- Insulation boards
- Shipping containers
- Use industry standard dimensions (like 20’, 4’x8’) to minimize customized production
- Modular design to minimize installation/integration effort
- Robust technology to minimize environmental requirements (temperature, pressure, humidity)
- Detector-building interplay: use detector as a structural support for the building?

## Constructing the detector ‘wall’

- Containment issue: need very large detector. Recall: K2K near detector – 1 kton mass, 25 tons fiducial, JHF proposal – 1 kton mass, 100 tons fiducial  need to understand in details
**Engineering/assembly/practical issues (just think about 7 stories tall thin wall of absorber!)**

**Solution: Containers ?**

## Absorber

- Particle board (or equivalent)
- Cheap
- Good mechanical properties. Can be used to build a self-supporting detector wall
- How long is the radiation length?? Assume 45 grams( like plastic), need to verify/measure.
- 1/3 radiation length sampling  15 grams ~ 20 cm ~ 8”

## Particle board

## Resistive Plate Counters (Virginia Tech, BELLE)

- Glass electrodes are used to apply an electric field of ~4kV/mm across a gap.  _(1mm? 2mm?)_
- The gap has a mixture of argon,isobutane and HFC123a gas. An ionizing particle initiates a discharge which capacitively induces a signal on external pickup strips.

- 5 years of tests in Virginia Tech, 4 years operating experience in Belle

## Why glass RPC’s?

- _Proven technology_ (BELLE). Glass avoids all  the problems associated with bakelite/lineseed oil at the price of poor rate capabilities => well matched to the experimental requirements
- _Two spatial coordinates_ from the same detector plane => maximize the topological information
- _Large signals_ with digital readout => easy and inexpensive electronics
- Easy to form long readout pads by connecting chambers => minimize electronics
- _Wide range of acceptable temperatures and pressures_ => minimize requirements for the building (RPC chambers proven to function down to –12oC, although glass resistivity changes by a factor of 40! Peter Mazur)

## Inductive strips readout board – Al Abashian

- Strip readout : transmission line using insulation board.
- Strips cut with a table saw

- Twisted pair cable + mass connector
- Copper pads glued to the board to facilitate cable attachment

## Transmission Line Impedance

- r

- Readout Strips

- Ground Plane

*Via G. Drake, from: “*Introduction to Electromagnetic Compatibility*”, Clayton R. Paul, 1992.*

**Notes:**
Check numbers of each type – need design parameter book

## Impedance Measurement

- Tune termination for each strip width to get 0 reflected signal for injected charge pulse
- Summer student Oluwaseun Amoda (EE undergrad from U. Memphis.)

- Input

-  open termination
- - best termination

- Front reflection

- Back reflection

- t (sec)

- I into 50  (V)

- Peter Shanahan, Valery Makeev, Olu Oamoda, Raoul Hennings

**Notes:**
Check numbers of each type – need design parameter book

## Impedance vs. Width

- General agreement with expected dependence of Z vs. x=w/h
- Z=62  for 3cm strip
- For 1⁄2” thick board

**Notes:**
Check numbers of each type – need design parameter book

## Chained Readout Boards

- Issues:
- Attenuation in board
- Impedance mismatch (and reflections) at internal boundaries
- Don’t expect it to be important for frequencies below *c*cable/*l*gap (more simply, won’t hurt if propagation across gap is faster than rise time ?)
- If so, allows up to O(0.5m) or so for interconnections.

- electronics

- Appropriate
- termination

- Optics analogue

**Notes:**
Check numbers of each type – need design parameter book

## Transmission Measurements

- 8 ft (2.44m)

- Measure charge collected from injected pulse as function of distance from readout end

- 10cm twisted pair

- Summer Student, Raul Hennings-Yeomans (Physics undergrad from U. Hermosillo, Mex.)

**Notes:**
Check numbers of each type – need design parameter book

## Transmission

- Less than 3% loss over 10 meters
- This is charge – didn’t keep track of peak voltage
- No specific effects due to strip interconnects are visible on scale of 1% uncertainties.

- ADC charge vs. distance (cm)

- Different symbols correspond to identical trials

**Notes:**
Check numbers of each type – need design parameter book

## Glass chamber + strips sandwich

- Large area glass RPC sandwiched between two readout boards: X and Y coordinate from a single chamber

## Storing and handling large glass chambers

- 29 large area GLASS RPC chambers from Virginia Tech

- Rotating table for handling the chambers

## Absorber+RPC module 

- Need to cover 2.4x6 m with glass chambers:
- 3  chambers 2x2.4 m?
- 2 chambers 3x2.4 m?
- 5 chambers 0.48x6 m?

## Mechanical prototype of the absorber+chamber module

##  Fundamental module

- 8’ wide x 20’ long x 9.5” thick (8” particle board + 2x0.5” insulation board + 1/3” RPC chamber)
- ~ 2 tons
- Robust unit, easy to handle. Sensitive items protected against posible mishaps.
- 3 chambers (2 x 2.4 m2)
- Gas and HV _daisy-chained?_ Separate lines?
- 80 x readout strips + 200 y readout strips
- 3 flat cables in x, 7 flat cables in y

## Mechanical prototype of the module

## Shipping unit: a container 

- _ISO specifications_
- Corner posts take load
- Corner blocks for rigging
- Corrugated steel sides & top
- Doors on one end (or more)
- Hardwood plywood floor sealed to sides
- Angle/channel steel support below floor, fork pockets

## Container == a complete piece of a detector

- 10 modules
- 20 tons
- 2000 y strips + 800 x strips
- 10 (30?) HV connectors (on both sides)
- 10 (30?) gas connectors (on both sides)
- 30 flat cables in x, 70 flat cables in y

## Assembling containers into a detector wall

- Version 1: readout at the periphery
- Connect x and y strips
- Daisy chain gas ?
- Daisy chain HV?
- Issue(?):
-  ‘buried’ cable and connectors
- Container walls are in the way: cut them out? Cut holes?
- Version 2: distributed electronics
- Front-end readout mounted directly on the readout boards. No cables or connectors
- Issue: cost of electronics

## Signal cables at the edge of a module

## Connecting strips across containers

- Position one container

- Bring neighboring container
- Connect the strips
- Close the gap

- Connecting containers requires 3 openings in side walls and 7 openings in top/bottom

## A container wall

- Stack 8 containers high and 4 containers wide wall  32 containers x 20 ton = 640 tons
- For 20 ktons one needs 31 container walls, or 992 containers
- Assuming 20 cm distance between walls it gives a detector which is 80 m long

## Production/construction scenarios

- Some labs construct ‘components’:
- Coated and tested glass
- Electronics
- Gas distribution
- HV distribution
- Some labs construct detector modules, insert into containers. Check out/calibrate the container-detector
- Containers are shipped to the detector site and integrated into the detector volume.

## Monolithic detector variant:

- Variant 1:
- Fundamental building blocks are constructed by gluing 1” boards displaced by 2(?)” in x and y. Modules are shipped in the containers. At the detector site the modules are assembled into a large plane in a lego-like fashion. Planes are cross-connected to provide stability. Uniform detector with no voids/dead spaces.
-  Variant 2:
- Modules are shipped in the containers, as always. Large rack is constructed to hold the modules and to provide the support for the building.

## Detector cost?

- Cost estimates make _little sense_ without a complete design of a detector including fabrication, testing and integration
- Cost estimate of a ’20 kton’ detector requires optimization of the longitudinal segmentation and (to a lesser degree transverse segmentation of the detector)
- What counts is fiducial mass, not a total mass. More detailed studies needed to understand the containment requirement
- A proposal: for the purpose of comparison assume:
- 1/3 Xo longitudinal segmentation (_in each view, _or demonstrate equivalence in electron ID efficiency)
- 3 cm strips
- 2 m cut around the edges (or 20x20 m detector)

## How many dimensions?

## Containerized RPC detector, salient features

- Uniform response over the entire volume (no factor 15 difference left-to-right, top-to-bottom)
- Fast response. Event integration time ~50 nsec. Factor of 200 better rejection against backgrounds than II/CCD
- Simple, reliable, easy to build detectors
- Relatively small modules to build and handle
- Utilize industrial solution for construction of a huge detector volume
- Minimize testing/calibration/integration by shifting these efforts to production centers (excellent opportunity to educate and train students!)
- Relatively simple and inexpensive transport
- Inexpensive electronics
- Wide range of environmental conditions acceptable

## Cost elements

- 120,000 m2 (== 400 m2 x 300 planes) of chambers  @ $150/ m2                                                 $18 M
- 1000 shipping containers              $2.5 M
- Particle boards                             $4.5 M
- 500,000 electronics channels ( 300 X [700+700]) @ $10/ch                                     $ 5M
- Gas system                                    $ 2M
- HV system                                     $ 3M
- Total ( so far)                                   $35 M

- Needs thought and ideas

## Conclusion

- Glass RPC + particle board + shipping containers offer a practical solution to a problem of constructing a huge volume detector
- Detector is modular with fundamental building blocks relatively simple to construct
- Industrial solutions used the challenging problem of scale
- Detector well suited for construction at a distributed centers
- Whereas the construction techniques exist, major cost savings can be, perhaps, realized with an additional effort towards industrialization of the glass chambers
- If not, what are the most obvious weaknesses?

## Questions

- is all this detector concept solid enough to claim ‘readiness’ for construction?
- If not, what are the most obvious weaknesses?