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

From Cuawiki

Line 35: | Line 35: | ||

::* back of box - adding shielding is difficult due to cables, high voltage, etc. Can add an incomplete shielding coverage on the back | ::* back of box - adding shielding is difficult due to cables, high voltage, etc. Can add an incomplete shielding coverage on the back | ||

− | * Discussion of predicting the impact | + | * Discussion of magnetic shielding and predicting the impact on magnetic field where the PMTs are |

− | ::* Rough estimate of 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 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 | ::* 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 | ||

− |

## Revision as of 15:28, 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 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