1. Value Engineering proposal: Putting APA’s on outside or put short drift cell on outside April 21, 2014, Post meeting rev. April 25, 2014 Russ Rucinski 3D modeling, Steve Hentschel 1

2. Motivation Current configuration has Cathode planes next to the cryostat wall. Two issues; 1.Cathode plane stores significant energy, 100 to 150 Joules which could potentially damage the membrane if there’s a discharge. 2.Cathode plane (~180 kV) must be ~36 cm from ground. This LAr buffer is dead. Anode planes or a cathode plane at a lower voltage can be closer ~10 cm. 2

3. Configuration: Current Design on April 1, 2014 C A C A C 85 cm to wall 55 cm to knuckle 40 cm to floor 26 cm to knuckle Current Configuration has more space on side than bottom. Too much distance on side, too little on bottom. Centerline Spacing: 3482.5 mm 85 Joules stored energy from CPA. See Bo Yu calc., total energy including field cage = 141 J 3

4. Centerline Spacing: 3645 mm C A C A C 53 cm to wall 36 cm to knuckle 53 cm to floor 36 cm to knuckle Spacing on side and bottom made the same. 36 cm = 180 kV/5 kV/cm Need to work on support rail design to get it closer to wall. 150 Joules stored energy from CPA only. Total with field cage is higher ~210 Joules based on Bo Yu calc. Configuration: Design for 5 kV/cm 4

5. A C A C A Centerline Spacing: 3741 mm 33 cm to wall 15 cm to knuckle 53 cm to floor 36 cm to knuckle Configuration: Anode Planes on Outside Extra row of Anode planes cost more. More LAr is instrumented. Need to work on rail design. Center APA’s may need to be thicker to get cables up. 20 Joules from CPA plane. 94 Joules total stored energy including field cage – see Bo Yu calculation 5

6. C A C A C A C Centerline Spacing: 130 mm Outer AC 3686 mm Inner AC 33 cm to wall 15 cm to knuckle 53 cm to floor 36 cm to knuckle 10 cm drift cell on outside Configuration: Short 10 cm Drift at Outside Can identify tracks from outside. Is this useful? 6

7. Summary of Configurations * Ignores phase change and changing Cp. melting point of stainless steel is 1650 K ConfigurationArrangement Wall knuckle to Outer row (mm) Cathode voltage (kV) Drift distance (mm) Fiducial Volume two detectors (kton) Energy on Cathode Plane (Joules) Temperatu re Rise of 2mm SS cube (K)* Design on April 1, 2014C A C A C687-1733452.510.25852700 Design for 5 kv/cm nominalC A C A C362-181361510.831504793 Anode planes on outsideA C A C A150-186371111.1820651 Short 10 cm drift at outsideC A C A C A C150-183365610.9820625 The conclusion is that we need anode planes on outside or short drift cell at outside to mitigate the stored energy risk. A physical test of a HV discharge with 150 Joules to a 1.2 mm membrane is planned at UCLA 7 Total stored energy higher, see Bo Yu calculations, LNBE docdb 8920

8. Change is close to cost neutral Design for 5 kV/cm nominal APA’s on outside Short drift cell on outside ConfigurationC A C A CA C A C ACA C A C AC Number of APA’s80120 Number of CPA’s12080160 Fiducial Volume for 2 detectors 10.8 kton11.2 kton11.0 kton Cost of APA construction $8.9M$12.7M Cost of Photon Detection system construction $4.8M$7.0M Cost of Cold Electronics construction $5.0M$6.5M Cost of CPA construction $2.9M$2.2M $3.6 M Subtotal Cost$21.6M$28.4M$29.8M Incremental CostBaseline$28.4-21.6=$6.8M$29.8-$21.6=$8.2M Total Cost for FD*$278M$278+$6.8=$285M$278+$8.2=$286M Cost per kton fiducial $25.7M$25.5M$26M Choose configuration and then adjust drift distance and cryostat size to get 10 kton 8

9. More work needed: Mounting rail design to hang APA or CPA closer to wall. Cabling, center APA’s different for cable routing? For short drift cell on outside, is this useful for physics? Cryostat dimensions – would change Optical coupling outer and inner TPC volumes Better understanding of High Voltage rules, max field. Understand discharge mechanism and speed of discharge. Understand impact of low energy background on SN physics. Understands physics benefit of a Veto region on outside. 9

10. Backup 10

11. HV to ground information Literature value breakdown at small distances, dirty LAr1000kV/cm Possible breakdown field in high purity liquid argon40kV/cmMicroBooNE docdb 3307 Possible breakdown field in gaseous argon30kV/cmLBNE docdb 4482 128 kV probe at 10 cm in 1 ppm O2 liquid argon okay12.8kV/cmMicroBooNE docdb 3246 ICARUS design, 75 kV at 30 cm2.5kV/cmICARUS communication ICARUS proof test in 2013, 150 kV at 30 cm5kV/cmICARUS communication MicroBoone maximum E design20kV/cmMicroBooNE docdb 3307 MicroBooNE, nominal max. gradient = 125 kV at 10 cm12.5kV/cm LBNE maximum E field design15kV/cmchosen by Russ Rucinski LBNE nominal maximum gradient, 180 kV at 36 cm5kV/cmchosen by Russ Rucinski 11 I have requested more information from MicroBooNE high voltage test cryostat and also from ICARUS.

12. Knuckle 12