Kara Hoffman The University of Chicago Enrico Fermi Institute

The challenge While disturbing the beam as little as possible measure: intensity size/profile (in 2 dimensions?) timing between bunches or pulses The detection medium must be radiation hard. The beam must be accurately measured in an environment with a lot of noise from rf cavities, etc. The profiler and associated readout/power cables must fit within the design of the cooling channel. Muons are difficult to detect.

IDEA #1

Bolometry: proof it works 0.8 V 0.8 V 10 ms Carbon 0.8 V 0.8 V 20 ms Nickel “bolometer” (actually a commercially made thin film nickel thermometer) Xe flashlamp lenses cryostat filter electronics Signal or background? Look for thermal dependence (i.e. change in signal size, time constant). Polarity: carbon’s electrical resistivity increases with temperature while nickel’s decreases. Signal or background? Look for thermal dependence (i.e. change in signal size, time constant). Polarity: carbon’s electrical resistivity increases with temperature while nickel’s decreases. (“homemade” from graphite foil or colloidal

Beamtests at ANL: setup copper block with 1/8 ” hole used to mask off beam and shield the thermometer Pulses nominally 10 nA in duration--we tried to reduce inductive noise by elongating pulses to lower instantaneous current beampipe cryostat temperature controller vacuum pump LH2 tank bolometric film /pulse Hz

@T=20K Beamtests at ANL: results RESULTS INCONCLUSIVE **It is difficult to separate inductive noise from a real thermometric signal.** Possible remedies: Use electronic filters to distinguish signal since thermal time constant should be much longer than the noise. Use two bolometric materials with opposite thermal response to subtract the noise. Use a material with a much larger thermal response. (i.e. a superconducting edge thermometer)

K  beam radius Signal expectation: the linac test facility GEANT3 simulation Corresponding % resistivity change in bolometer strip Platinum TCR curve

Advantages: doesn’t disturb the beam relatively inexpensive robust Drawbacks: must be applied to absorber window for heat sinking – could be an issue mechanically/safetywise and cannot be removed or replaced small signal, particularly for more diffuse beams metal strips provide challenge in large electromagnetic noise environment large thermal time constants do not allow for measurement of timing information Bolometry findings Evolution of window design has produced thinner prototypes

Diamond is prized for more than just its sparkle (high refractive index)… low leakage I very fast readout no p-n junction needed low capacitance rad hard, strong no cooling hard insensitive to  ’s >220nm Makes a great particle detector! The RD42 collaboration (CERN) has been developing diamond (primarily) as a microvertex detector.

diamond substrate ~500  m thick (when used as a microvertex detector) E (>1 V/  m) sputtered metal strips/pixels (400 angstroms of titanium or chromium coated with 4000 angstroms of gold) solid electrode Ionizing radiation (36 e-h pairs per m per mip) Anatomy of a diamond substrate microstrip detector… Essentially a very compact solid-state ionization chamber. IDEA #2

Diamond as a beam profiler? sensitive (2 coordinate?) measurement fast (subnanosecond ~40ps) intrinsic response might allow temporal beam profiling, in addition to current and position measurements free standing-accessible low Z- very little beam loss has been demonstrated to be rad hard to a proton fluence of at least relatively huge signal (too huge??) Diamond has not yet been realized as a microvertex detector because the signal size is small compared with silicon and single particle detection efficiency is required. However, single particle efficiency is NOT required for a beam profiler.

Polycrystalline CVD Diamond growth side substrate side induced charge: dx= distance e-holes drift apart  = carrier mobility,  = carrier lifetime Carrier lifetime effected by: size of individual crystals- grain boundaries in grain defects and impurities

tails due to carrier lifetimes Charge collection efficiency Charge collection efficiency is a product of:  d -carrier drift velocity- a function of the applied electric field up to a saturation velocity  -carrier lifetime-a function of diamond quality- commercially available diamond improving with time

“black” diamond polished high purity diamond unpolished diamond diamond membrane (with person peeping through) What kind of diamond is best suited as a beam profiler? signal size could be limited by decreasing the electric field this approach is destructive to timing information diamond with short carrier lifetime small  gives faster response at the expense of efficiency much cheaper as thin as possible less charge produced per mip voltage required for maximum carrier velocity is proportional to thickness easier to dissipate heat diamond “membranes” can be made 1  m thick We want to minimize the signal while exploiting the timing information.

Detector fabrication: sputtering electrodes We have fabricated our first prototype from a piece of 500  m x 11mm x 11mm detector grade CVD diamond that was manufactured by DeBeers. Leads were sputtered at OSU using a shadow mask—finer segmentation could be achieved with a lithographic mask.

Towards a diamond testing program… R&D areas: Application specific material will need to be developed, along with fast electronics. Over what range of intensity measurements could diamond be useful? (space charge effects?) How radiation hard is it? Near term plans: We are in the process of obtaining some diamond with shorter carrier lifetimes. We plan to study the behavior of our prototype in a beam test at Argonne this summer. R&D areas: Application specific material will need to be developed, along with fast electronics. Over what range of intensity measurements could diamond be useful? (space charge effects?) How radiation hard is it? Near term plans: We are in the process of obtaining some diamond with shorter carrier lifetimes. We plan to study the behavior of our prototype in a beam test at Argonne this summer.

Two novel concepts for beam profiling are being studied/developed at the University of Chicago. The signal to background ratio for bolometry may be too low for use in a muon cooling channel or test facility.Two novel concepts for beam profiling are being studied/developed at the University of Chicago. The signal to background ratio for bolometry may be too low for use in a muon cooling channel or test facility. If CVD diamond is demonstrated as a viable beam profiling medium, it may find applications outside of the muon collaboration.If CVD diamond is demonstrated as a viable beam profiling medium, it may find applications outside of the muon collaboration. The Fermilab beams division has shown a keen interest in the outcome of CVD diamond beam tests and has offered supplies as well as technical support. The Fermilab beams division has shown a keen interest in the outcome of CVD diamond beam tests and has offered supplies as well as technical support. The first prototype diamond profiler has been fabricated and a beam test is being planned for the summer.The first prototype diamond profiler has been fabricated and a beam test is being planned for the summer.