Putting Foils on the DUNE CPA Introduction We are setting up a - PowerPoint PPT Presentation

Putting Foils on the DUNE CPA

Introduction ● We are setting up a small working group to develop the method of installing WLS-coated reflector foils on the CPA. ● There is some R&D, tests and engineering work that needs to be done. ● This talk is a summary of things that were discussed or are happening. – Matching WLS with ARAPUCA coating – Considerations about putting foils on DUNE CPA. ● Get in touch with me, if you'd like to get involved help out ( andrzej.szelc@manchester.ac.uk ) 2

Matching WLS between foils and ARAPUCA ARAPUCA coating→ pT TPB PEN Other Foil Coating pTerphenyl TPB Starting Point PEN Other 3

General comments ● ARAPUCA covered with same WLS as ARAPUCA – potentially best light collection efficiency (provided transparency of WLS on ARAPUCA is high – preparing measurements of TPB, PEN, pT on glass). ● ARAPUCA covered with a WLS “lower” than the foils – potentially good collection as well, although might have a 50% backwards effect. ● ARAPUCA covered with a WLS “higher” than the foils – lower light collections (ARAPUCA blind to reflected light) – need to add a lower filter version of ARAPUCA's (potentially no WLS on outside). 4

Tentative Light Yield Plots Assuming 2.5% ARAPUCA efficiency. Leaving some ARAPUCA's uncoated on purpose to get uniform collection (not best case scenario) Daniel Cookman, Manchester 5

Tentative Light Yield Plots 2 Assuming 2.5% ARAPUCA efficiency. Leaving some ARAPUCA's uncoated on purpose to get uniform collection (not best case scenario) Daniel Cookman, Manchester 6

ARAPUCA covered with pT ● Current baseline design. Then: – Foils covered with pT: ● According to measurements, foils won't work at pT wavelenghts. ● Also, no experience with foils covered with pT. – Foils covered with TPB ● ARAPUCA's blind to reflected light (exclusive case). ● Known technology. – Foils covered with PEN ● ARAPUCA's blind to reflected light (exclusive) ● Need to figure out coupling to foils, and behaviour in cold. ● Need to measure performance on foils (in progress) ● Potentially could make foil preparation much easier. – Foils covered with “other”. Bis-MSB? ● Would need aging/behaviour in cold studies. Bis- MSB less efficient than TPB for VUV. 7

ARAPUCA covered with TPB ● Need a different WLS on the inside (ELJEN green?) – Foils with pT, see previous slide. Also 50% backwards efficiency, probably not very useful. – Foils with TPB ● ARAPUCA's sensitive to reflected light (inclusive case, possibly with a small correction – measurement being set up). ● Known technology. – Foils with PEN ● ARAPUCA's sensitive to reflected light (inclusive case, possibly with a small correction – measurement being set up). ● Need to figure out coupling to foils, and behaviour in cold. ● Need to measure performance on foils (in progress) ● Potentially could make foil preparation much easier. – Foils with Other? ● Would need aging/behaviour in cold studies. Bis-MSB less efficient than TPB for VUV. 8

ARAPUCA covered with PEN ● Similar wavelengths to Kuzniak & Broerman arXiv:1806.04020 TPB. Would need R&D to develop coupling method. Not sure this is useful given the area of ARAPUCA's (evaporation is viable). ● Foils cases similar as per TPB. 9

ARAPUCA covered with other (bis-MSB?) ● Bis-MSB efficiency measured by Ettore et al. Looks comparable to TPB at visible, but worse at VUV. Not as useful. ● Foil considerations then similar to TPB and PEN. 10

Foil and ARAPUCA WLS matching ARAPUCA coating→ pT TPB PEN Other Foil Coating pT X X X X TPB Current: LY. Incl. X X LY excl. – need WLS R&D on inside of AR. PEN LY excl. LY Incl. (similar for PEN) X X Some R&D - need WLS R&D needed for on inside of AR. PEN Other X X X X 11

D i e l e c t r i c b r e a k d o w n s t u d i e s +HV • f o i l s o n c a t h o d e w i l l n e e d t o t o l e r a t e s o m e c h a r g e b u i l d - u p o r v o l t a g e v a r i a t i o n - e g 0 . 5 c m p e r f o r a t i o n s l e a d t o 3 0 0 V v a r i a t i o n o n f o i l s u r f a c e ( f r o m s i m u l a t i o n s ) • C h e c k e d H V b r e a k d o w n s t r e n g t h a c r o s s fj l m / f o i l s a m p l e s s u b m e r g e d i n L N - s a m p l e s s a n d w i c h e d b e t w e e n 6 c m d i a m e t e r e l e c t r o d e s - s t e p p e d u p v o l t a g e u n t i l b r e a k d o w n o c c u r r e d Clark Griffith, 1 2 1 8 / 0 9 / 1 8 Sussex

CPA with Refmector Foil Concept • The goal is to preserve the current CPA construction as much as possible, and to provide the option of implementing the refmector foils post CPA production. • The preferred solution is to maintain the current CPA design, and include a set of attachment holes on each CPA resistive panel to allow the installation of refmector foils in smaller tiles on both sides of the CPA surfaces at ITF or in the UG cleanroom. From Bo Yu, and Francesco 13 Pietropaolo

Refmector module option 1: • Construction: Laminate the 3M refmector foil on a thin FR4 backing sheet, evaporate TPB on the refmector surface, mount the reinforced refmector foil on the CPA panel. • Pros: simple construction, no CTE mismatch • Cons: high likelihood of surface charging on the refmector foil and results in sporadic breakdowns through the refmector sheet From Bo Yu, and Francesco Pietropaolo Potential distribution on a 8cm square fully charged refmector foil. The maximum voltage at the center of the foil is 1.6kV. Potential contours and drift lines on a vertical cut plane diagonal of the foil. 14

Refmector module option 2: • Construction: Evaporate TPB on the 3M refmector foil, Enclose the refmector foil on the CPA surface with a metal wire mesh frame. The wire mesh will bleed the charge to the resistive CPA channel. • Pros: Solves the charge up problem; relatively simple construction • Cons: Reduces the efgectiveness of the current resistive CPA design due to the large conductive areas • Remedy: use insulating frame to hold the wire mesh, use 2 (redundant) closely spaced electrical contacts to the CPA surface. From Bo Yu, and Francesco Pietropaolo 15

Refmector module option 3: • Construction: Laminate the 3M refmector foil on a thin FR4 backing sheet, perforate the lamination with an array of holes to expose the resistive surface on the cathode, evaporate TPB on the refmector surface, mount the reinforced refmector foil on the CPA panel. • Pros: reduces the magnitude of surface charging to avoid breakdown and drift fjeld distortion • Cons: more complex construction; reduced refmector coverage From Bo Yu, and Francesco Pietropaolo Potential distribution on a 1cm square cell with 5mm hole. The maximum voltage at the corners of the cell is 290V. Potential distribution on a 1cm hex cell with 5mm hole. The maximum voltage at the corners of 16 the cell is 220V.

Refmector module option 4: • Assumption: Availability of a transparent and resistive plastic sheet (~1mm thick), either surface or bulk conductive. The resistivity should be no less than that of the CPA panel. • Construction: Evaporate TPB on the resistive side of the transparent plastic sheet (if surface conductive only), encase the 3M refmector foil on the CPA panel by the resistive plastic sheet. • Pros: no charging, no degradation of the CPA resistive property • Cons: the transparent resistive material has not been identifjed; CTE mismatch From Bo Yu, and Francesco 17 Pietropaolo

Tests/R&D/needed ● Ting has found acrylic that is resistive. We now have a copy and will test how evaporation works on it and how it performs (option 4). ● Will be measuring transmittance at visible light of TPB covered glass, 450 nm filter, and reflectance of pT covered foils. ● Plan to test performance of foils on CPA in CERN test stand – talking to Francesco to establish time, likely to be late November time frame. ● Next steps – looking into DAB tests, and protoDUNE run II tests. ● In parallel, simulations ongoing to repeat performance studies being done without foils. ● Engineering: design of a 4Pi evaporator. Could use crucible design from DEAP, need to design a structure that holds plates in 4Pi, and a walk in cryostat to hold it. 18

Conclusions ● Gearing up to define the method to install WLS- covered reflector foils on the CPA. ● Help is needed, please get in touch with me if you would like to contribute. 19