PASI 2013, 3 rd – 5 th April 2013, RAL 03-Apr-2013Fergus Wilson, STFC/RAL1 UK Silicon Digital Calorimetry

Digital Calorimeter (DECAL) 03-Apr-2013Fergus Wilson, STFC/RAL2 Make a pixellated calorimeter to count the particles. Binary readout i.e. hit/no hit. Pixels need to be small enough to avoid multiple particles passing through the same pixel. 100 particles/mm 2 leads to pixel sizes of 50 μm 2. Higgs Factory ECAL would need channels. Dead area and power consumption must be kept to a minimum.

Silicon Pixel Detector Research SpiDer Created following demise of Linear Collider R&D in the UK (~2007) Univ. of Birmingham, Bristol, Oxford, Imperial College, Queen Mary, and RAL/STFC. Goal: Develop monolithic active pixel CMOS sensors (MAPS) for future experiments and to demonstrate their viability for vertexing, tracking and calorimetry applications. – Granularity, speed, power, material budget, radiation hardness Still aimed at linear collider (CALICE-UK) but with an eye on medical, nuclear and other particle physics experiments. 3-yr, 9 FTE, £3M project request went in Project informally approved 1 st April 2009 then formally cancelled 4 th April Apr-2013Fergus Wilson, STFC/RAL3 VertexingTrackingCalorimetry Pixel size (um) Spatial occupancy (/mm 2 ) Material per layer (X0)< 0.1%<1% Output signal>5 bit analogueAnalogue or binarybinary Noise (MIP)<0.1

Monolithic Active Pixel Sensors (MAPS) Standard CMOS process (=> low cost) – 180 nm; 6 metal layers; Precision Components – Low leakage diodes; – 5/12/18 μm epitaxial layers. Very thin overall. Additional Features developed: – Deep p-well : improved charge collection. – High resistivity epitaxial layer : radiation hardness. – 4T Structures : In-pixel double count sampling (DCS), low noise, low power (<10μW/pixel). – Stitching : large structures (5 cm x 5 cm has been achieved). 03-Apr-2013Fergus Wilson, STFC/RAL4

Sensor Development Timeline Rough Time-line Calorimetry TPAC 1.0TPAC 1.1TPAC 1.2 Tracking Fortis 1.0Fortis 1.1 Cherwell 1.0 Cherwell 2.0 Vertexing Cherwell 1.0 MAPS Technology Deep p-well High Res4TStitching Rad. Hard. (medium) 03-Apr-2013Fergus Wilson, STFC/RAL5

SPiDeR prototypes Build 3 chips: ISIS (vertexing), TPAC (calorimetry), Cherwell (tracking). By time SpiDer cancelled all chips made but only ISIS characterized. 03-Apr-2013Fergus Wilson, STFC/RAL6 ISISTPACCherwell Charge CollectionPhotogate + CCD register 4 diodes plus >100 transistors /pixel Pinned Photodiode (4T) Pixel size (um) (50) Time slicingX 20 in-situ storage cells X 8192 time stampX10 rolling shutter Noise MinimisationRaw charge storage and CDS signal shaping and pseudo-CDS CDS Power Minimization Delayed slow readout (rolling shutter) Asynchronous operation Rolling shutter Radiation ToleranceHigh resistivity study to enhance tolerance Yield and costCustom CMOSStandard CMOS

Tera-Pixel Active Calorimeter Sensor (TPAC) 03-Apr-2013Fergus Wilson, STFC/RAL7 1 cm

TPAC 55 Fe and IR laser results F B Pixel profiles Using 55 Fe sources and IR lasers  Using the test pixels (analog output)  IR laser shows impact of deep p-well implant 03-Apr-2013Fergus Wilson, STFC/RAL8

TPAC test-beam CERN/DESY Apr-2013Fergus Wilson, STFC/RAL9

TPAC Pixel efficiency 03-Apr-2013Fergus Wilson, STFC/RAL10

TPAC Shower Multiplicity 03-Apr-2013Fergus Wilson, STFC/RAL11 Shows correct behaviour as function of energy. Demonstrates DECAL concept validity

Out of the fire (2011) 03-Apr-2013Fergus Wilson, STFC/RAL12 Generic R&D program. Targetted: Flavour factories, ALICE upgrade and T2K upgrade 1.25yr, 2 FTE, €500k requested. Awarded Dec Funding ends: April 6 th 2013

The Cherwell Chip 13 Cherwell Digital Calorimetry (DECAL) “4T” pixels with triggered global shutter and in-pixel CDS 25um pixel pitch 2x2 pixel summing at column base [96x192 pixels] 50um pixel pitch [48x96] Vertex Tracking Standard “4T” pixels Reference pixel array 12 bit ramp ADC implemented at column base [48x96] “Strixel” array 12 bit ramp ADC in pixel array [48x96] 4 Blocks 3 Variants 03-Apr-2013Fergus Wilson, STFC/RAL

Maximising the fill factor 14 The efficiency of a detector is dependent on how much of the surface area is occupied by dead space. Core part of the design of Cherwell is to use islands of electronics within the pixel array – avoid having dead regions at the edge of a sensor to maximise sensitive area. 4T4T SELECT COL RESET COL 1x SR AM BIAS COL 4T4T 4T4T 4T4T 4T4T 4T4T 4T4T 4T4T 4T4T 03-Apr-2013Fergus Wilson, STFC/RAL

Laboratory Tests – Cherwell Variants All the following results are from the last month. Analysis is still on-going. 03-Apr-2013Fergus Wilson, STFC/RAL15 Noise per pixelFull well per pixel New Implant = low noise variant

Temperature variation 16 Performance of the pixels changes as a function of temperature: – Want to understand how things vary over a sufficient range for a viable system: T = [-50, +50] °C. – Believe we can go lower. Have gone down to 77K without problem. – More tests in the Summer – Could be useful for cryogenic detectors. High Res Epitaxial Layer Expected behaviour up to ~50°C Good operating range 03-Apr-2013Fergus Wilson, STFC/RAL Stable

Cherwell PTC Characterisation work 17 RMS Noise(e) per pixelGain (ADCs/e) per pixel Signal Log(Signal) Log(Noise 2 ) Noise 2 Good Uniformity

18 Cherwell Test beam CERN Nov T4 beamline at H6 at CERN 1 week of 120 GeV π beam time Aim: understand resolution, charge sharing, and efficiency of Cherwell. p ~ 120 GeV/c Δp/p ~1.5% 03-Apr-2013Fergus Wilson, STFC/RAL

Cherwell Correlation Plots Fergus Wilson, STFC/RAL19 S1:S2 S3:S4 S5:S6 S2:S3 S4:S5 S1:S6 Row Number 03-Apr-2013 Position resolution analysis still on-going Hoping for < 8μm resolution.

Cherwell initial Cluster analysis Seagull plot showing where charge is added to a hit Shows that charge is spread between more clusters in standard resistivity sensors Looking at the size of clusters (lower plot) charge is also more often in larger clusters 03-Apr-2013Fergus Wilson, STFC/RAL20

MAPS exploitation from STFC 03-Apr-2013Fergus Wilson, STFC/RAL21 Rad tolerant, low noise Highly Miniaturised Radiation Monitor (HMRM) for ESA Achilles : Rad hard 16M pixels for Transmission Electron Microscopy (TEM). Lassena : 6M pixels for X-ray imaging. 3-side buttable Kirana: >10 6 frames per second

Near Future : Cherwell 2 and ALICE 03-Apr-2013Fergus Wilson, STFC/RAL22 Using the Arachnid project expertise and funding, developed a new sensor prototype at RAL for use on ALICE Inner Tracker System upgrade. – Out for production: 12 th March – Testing at DESY: June-July. – Technology decision : Fall. – TDR : Winter. – Our participation depends on receiving STFC funding in 2013 (and beyond…). ALICE ITS requirements surprisingly similar to CLIC vertex detector specifications.

UK MAPS Near Future 2013 DAQ/Test bench setup – Our current system is too slow and out of date. Looking at Commercial development systems: (e.g. Xilinx SP605). LHC system : ATCA/μTCA + GLIB card + Connector board. Digital ECAL MAPS (Cherwell 1 / DECAL) – Have the chips in hand. – Needs some tuning/FPGA work. – Hope to test at DESY June. – Hope to fund from STFC Particle Physics Department New Detector Initiatives. ALICE MAPS sensor (Cherwell 2) – Out for production: 12 th March – Testing at DESY: June-July. – Technology decision : Fall. – TDR : Winter. 03-Apr-2013Fergus Wilson, STFC/RAL23

UK and STFC facilities/interest Interest from UK universities in the technology for multiple purposes: nuclear, dark matter, medical, astronomy, commercial,…. STFC in-house facilities – Sensor Design – Technology Division (TD) – Good relationship with CMOS foundry (TD) – Wire bonding facilities, etc… – DAQ / Test bench (PPD) – Testing facilities 55 Fe irradiation, X-ray radiation, IR laser. Good relationship with DESY/CERN for test beams. 03-Apr-2013Fergus Wilson, STFC/RAL24

Conclusion MAPS has shown itself to be: – Versatile; fast; radiation hard; temperature tolerant; low power (passive cooling); low noise; potentially cheap to produce. Characterisation of Cherwell 1 on-going. We hope to test Cherwell 1 Digital Calorimeter block DECAL at DESY in Summer We hope to be involved in testing of ALICE Cherwell 2 chip. We hope to get funding to develop sensor for ITS ALICE => could be first large scale pixel detector using this technology. Particle Flow algorithms continue to be maintained and developed at Universities. We’ve kept the work going by being generic and then producing spin-offs (e.g. ALICE). Open to other MAPS exploitation proposals. MAPS is no longer the technology of tomorrow. 03-Apr-2013Fergus Wilson, STFC/RAL25