# Difference between revisions of "General Meeting Summary 10/31/19"

From Cuawiki

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::* Rough estimate of front magnetic shielding needed: | ::* Rough estimate of front magnetic shielding needed: | ||

::::* Transverse size of the box is 60cm (30 crystals at 20cm each) | ::::* Transverse size of the box is 60cm (30 crystals at 20cm each) | ||

− | ::::* Typical PMT shielding expectation is to extend shielding by 1 radius of the photocathode (here use the transverse size of the box) | + | ::::* Typical PMT shielding expectation is to extend shielding by 1 radius of the photocathode (here use half of the transverse size of the box) |

::::* Need to extend front shielding by ~30cm | ::::* Need to extend front shielding by ~30cm | ||

::* Back shielding | ::* Back shielding | ||

Line 44: | Line 44: | ||

::::* can leave top/bottom open for ventilation - a hole of 1cm ever two centimeters giving a fractional opening of 50% should be ok for magnetic shielding. Note that could increase the thickness | ::::* can leave top/bottom open for ventilation - a hole of 1cm ever two centimeters giving a fractional opening of 50% should be ok for magnetic shielding. Note that could increase the thickness | ||

::* Once decide where all shielding is located (geometry) can do a numerical calculation | ::* Once decide where all shielding is located (geometry) can do a numerical calculation | ||

− | ::* Based on numerical calculation can also determine if need additional front shielding | + | ::* Based on numerical calculation can also determine if need additional front shielding - may not be needed as long as have extended shielding, impact on resolution small, since have radiation shielding anyway |

+ | ::* Shielding around magnet to reduce transverse field is difficult - try to avoid | ||

+ | |||

+ | * Action Items: | ||

+ | ::* Finalize shielding dimensions | ||

+ | ::* Numerical calculations of magnetic field with additional shielding | ||

+ | |||

+ | |||

+ | FRAME - AIR CIRCULATION | ||

+ | |||

+ | * Hycal and NPS prototype used nitrogen purge | ||

+ | |||

+ | * Dry air could work too to remove moisture. Also note that temperature of NPS will be 18 degC compared to 14 degC of HyCal | ||

+ | |||

+ | |||

+ | SIMULATIONS - SOURCE OF RADIATION IN HALL C | ||

+ | |||

+ | * Geant4 simulation for source tracking developed | ||

+ | ::* includes NPS in Hall C geometry | ||

+ | ::* includes magnetic field map, but NOT the one that includes a magnetic beam pipe for shielding and proper propagation to the beam dump | ||

+ | |||

+ | * Validation: Results show that the major sources of radiation are the target and the next critical radius (here, beam pipe 2) | ||

+ | ::* consistent with expectation for any beam calculation - expect ~1/3 of radiation from these sources | ||

+ | ::* observation that have a source from top/bottom of pipe consistent with vertical bend magnet | ||

+ | ::* What fraction of background radiation is produced in a specific area? | ||

+ | |||

+ | * Simulate the shielding in front of the calorimeter with a cut of 10 MeV on the calorimeter distribution | ||

+ | ::* Should check the Geant4 default cut - likely is ~100keV | ||

+ | ::* Analyze the fraction of particles with <10 MeV and >10 MeV | ||

+ | ::* if only have 10 MeV particles can shield | ||

+ | |||

+ | * Results indicate not much reduction in background radiation even with shielding | ||

+ | ::* seems counter-intuitive | ||

+ | ::* what magnetic field was used? - need to use the one where have shielding around beam pipe 2 | ||

+ | ::* discussion about Opera plots of magnetic field - even after magnet there is a big spike (large fields), so need additional shielding | ||

+ | ::* additional shielding was implemented in form of a magnetic beam pipe | ||

+ | |||

+ | * Action Items: | ||

+ | ::* Include corrected field map | ||

+ | ::* Page 4: make 1D histogram to determine where one has to pay attention | ||

+ | |||

+ | |||

+ | CRYSTALS | ||

+ | |||

+ | * 64 additional Crytur crystals arrived and have been tested - total number: 414 | ||

+ | |||

+ | * Additional 40 crystals from Crytur are on the way | ||

+ | |||

+ | |||

+ | CRYSTAL PUBLICATION | ||

+ | |||

+ | * Draft will be circulated in week 11/4 for comments | ||

+ | |||

+ | |||

+ | COLLABORATION MEETING: 3 FEBRUARY 2020 AT JLAB | ||

+ | |||

+ | * Draft agenda will be subject of discussion for next NPS phone meeting | ||

+ | |||

+ | * So far suggested agenda items - please send additional suggestions for agenda items to hornt@cua.edu | ||

+ | ::* Magnet mapping results | ||

+ | ::* HV dividers | ||

+ | |||

+ | |||

+ | NEXT MEETING: THURSDAY 21 NOVEMBER AT 9:00AM (ET) |

## Latest revision as of 16:34, 1 November 2019

MAGNET

- ODU mapping tests ongoing

HV DIVIDERS

- All dividers are assembled at Ohio U!

- 2/3 of the dividers have been tested

- Discussion about divider non-linearity and impact on physics

- Level of non-linearity should be less than calorimeter resolution, e.g. if ~<1% non-linearity, then should not affect resolution
- Based on prototype beam tests, the bypassed version of the amplifier gives the expected resolution

- design acceptable since resolution ~1%
- will have effect on positioning, but an be corrected offline - more important is that the PMT survives (anode current ~<100ua)

- How well can non-linearity be measured? - if known well enough then an always correct

- Discussion about three new (reduced gain) divider designs recently made by V. Popov

- Test with LED - find average current of PMT, need to know anode current of PMT
- Take same PMT and check different types of dividers, e.g. bypassed vs. reduced gain, any improvements?

- Action Item: Collect information for all existing dividers

- resolution
- non-linearity

FRAME - MAGNETIC SHIELDING STUDY

- Comparing PMT specs and field map suggests that with shielding the field is 50G (transverse) and ~100G (longitudinal), so a significant effect --> must pay attention to shielding

- current shielding: 1mm mu metal around PMT
- consider adding soft iron and perhaps additional mu metal around entire box including crystals

- Discussion of mechanical aspects of adding shielding around the box

- distance front plate to PMT is 20.3cm - adding shielding should be fine
- back of box - adding shielding is difficult due to cables, high voltage, etc. Can add an incomplete shielding coverage on the back

- Discussion of magnetic shielding and predicting the impact on magnetic field where the PMTs are

- Rough estimate of front magnetic shielding needed:

- Transverse size of the box is 60cm (30 crystals at 20cm each)
- Typical PMT shielding expectation is to extend shielding by 1 radius of the photocathode (here use half of the transverse size of the box)
- Need to extend front shielding by ~30cm

- Back shielding

- may not need full 30cm extension since field smaller
- can leave top/bottom open for ventilation - a hole of 1cm ever two centimeters giving a fractional opening of 50% should be ok for magnetic shielding. Note that could increase the thickness

- Once decide where all shielding is located (geometry) can do a numerical calculation
- Based on numerical calculation can also determine if need additional front shielding - may not be needed as long as have extended shielding, impact on resolution small, since have radiation shielding anyway
- Shielding around magnet to reduce transverse field is difficult - try to avoid

- Action Items:

- Finalize shielding dimensions
- Numerical calculations of magnetic field with additional shielding

FRAME - AIR CIRCULATION

- Hycal and NPS prototype used nitrogen purge

- Dry air could work too to remove moisture. Also note that temperature of NPS will be 18 degC compared to 14 degC of HyCal

SIMULATIONS - SOURCE OF RADIATION IN HALL C

- Geant4 simulation for source tracking developed

- includes NPS in Hall C geometry
- includes magnetic field map, but NOT the one that includes a magnetic beam pipe for shielding and proper propagation to the beam dump

- Validation: Results show that the major sources of radiation are the target and the next critical radius (here, beam pipe 2)

- consistent with expectation for any beam calculation - expect ~1/3 of radiation from these sources
- observation that have a source from top/bottom of pipe consistent with vertical bend magnet
- What fraction of background radiation is produced in a specific area?

- Simulate the shielding in front of the calorimeter with a cut of 10 MeV on the calorimeter distribution

- Should check the Geant4 default cut - likely is ~100keV
- Analyze the fraction of particles with <10 MeV and >10 MeV
- if only have 10 MeV particles can shield

- Results indicate not much reduction in background radiation even with shielding

- seems counter-intuitive
- what magnetic field was used? - need to use the one where have shielding around beam pipe 2
- discussion about Opera plots of magnetic field - even after magnet there is a big spike (large fields), so need additional shielding
- additional shielding was implemented in form of a magnetic beam pipe

- Action Items:

- Include corrected field map
- Page 4: make 1D histogram to determine where one has to pay attention

CRYSTALS

- 64 additional Crytur crystals arrived and have been tested - total number: 414

- Additional 40 crystals from Crytur are on the way

CRYSTAL PUBLICATION

- Draft will be circulated in week 11/4 for comments

COLLABORATION MEETING: 3 FEBRUARY 2020 AT JLAB

- Draft agenda will be subject of discussion for next NPS phone meeting

- So far suggested agenda items - please send additional suggestions for agenda items to hornt@cua.edu

- Magnet mapping results
- HV dividers

NEXT MEETING: THURSDAY 21 NOVEMBER AT 9:00AM (ET)