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

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(Created page with "MAGNET * ODU mapping tests ongoing HV DIVIDERS * All dividers are assembled at Ohio U! ::* 2/3 of the dividers have been tested *") |
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::* 2/3 of the dividers have been tested | ::* 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 predicting the impact of (additional) shielding on overall magnetic field where the PMTs are | ||

+ | ::* Rough estimate of 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) | ||

+ | ::* 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 | ||

+ | ::* |

## Revision as of 14:19, 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 predicting the impact of (additional) shielding on overall magnetic field where the PMTs are

- Rough estimate of 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)

- 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