Hafnium Films and Magnetic Shielding for TIME, A mm-Wavelength Spectrometer Array

• Published in: Journal of low temperature physics Vol. 193; no. 5-6; pp. 893 - 900
• Main Authors: Hunacek, J., Bock, J., Bradford, C. M., Butler, V., Chang, T.-C., Cheng, Y.-T., Cooray, A., Crites, A., Frez, C., Hailey-Dunsheath, S., Hoscheit, B., Kim, D. W., Li, C.-T., Marrone, D., Moncelsi, L., Shirokoff, E., Steinbach, B., Sun, G., Trumper, I., Turner, A., Uzgil, B., Weber, A., Zemcov, M.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-12-2018; Springer Nature B.V
• Subjects: Bolometers; Characterization and Evaluation of Materials; Computer simulation; Condensed Matter Physics; Finite element method; Gold; Hafnium; Ionization; Legs; Low temperature physics; Magnetic Materials; Magnetic shielding; Magnetism; Physics; Physics and Astronomy; Red shift; Silicon nitride; Spectrometers; Variation; Transition-edge sensors; Bolometers; Spectrometers; Hafnium; Magnetic shielding
• ISSN: 0022-2291; 1573-7357
• DOI: 10.1007/s10909-018-1906-3

TIME is a mm-wavelength grating spectrometer array that will map fluctuations of the 157.7-
μ
m
emission line of singly ionized carbon ([CII]) during the epoch of reionization (redshift
z
∼
5–9). Sixty transition-edge sensor (TES) bolometers populate the output arc of each of the 32 spectrometers, for a total of 1920 detectors. Each bolometer consists of gold absorber on a
∼
3
×
3 mm silicon nitride micro-mesh suspended near the corners by 1
×
1
×
500
μ
m silicon nitride legs targeting a photon-noise-dominated NEP
∼
1
×
10
-
17
W
/
Hz
. Hafnium films are explored as a lower-
T
c
alternative to Ti (500 mK) for TIME TESs, allowing thicker support legs for improved yield. Hf
T
c
is shown to vary between 250 and 450 mK when varying the resident Ar pressure during deposition. Magnetic shielding designs and simulations are presented for the TIME first-stage SQUIDs. Total axial field suppression is predicted to be
5
×
10
7
.