Zoom into Research

Jia is the founding director of newly established Center for Data Driven Discovery (CD3) in Kavli IPMU. Congratulations and we will push D3 from CMB!

After the workshop, many scientists visit Kavli IPMU, we warmly welcome and introduce our experimental labs (PMU, AR coating, SO's baffle) to scientists from the workshop.

Very successful workshop with many participants from all over the world! Jia initiated and organized this workshop, and Toshiya, Hideki, Joaquin, Thuong have presented their works, and Elisa and Tomo joined to chair the sessions. Congratulations for the successful workshop and hope to have another one like this! URL: https://www2.yukawa.kyoto-u.ac.jp/~cmb-lss/index.php

Not sure when exactly, but we had a visitor from France... in fact, Hideki brought her from Europe. Is it her? A hat in French is "le chapeau"... 

Appearently, this is an French olympic mascot following the famous hat of her, https://en.wikipedia.org/wiki/Liberty_Leading_the_People

We are welcoming four ILANCE intern students:

• Julien Tang from École Polytechnique (left up) 

• Valentin Carpintero Pérez from École Polytechnique (left right) 

• Yona Lapeyre from ENS de Lyon (left bottom) 

• Albert Plerre Andre Bonnefous Abiven from LPTEN. (right bottom) 

Looking forward to working with you for next 4 months!

Kosuke Aizawa and Ryosuke Akizawa have arrived at Dept. of Physics at the Univ. of Tokyo as first-year master's students. Looking forward to working and studying together!

Ryota has newly started as the JSPS postdoc at Kavli IPMU. He has an office now!

Many congratulations for the happy retirement! Thank you very much for Nobu to built this CMB group at Kavli IPMU. With your tremendous efforts, we now have the new IPMU CMB community! We hope you can continue to support us! 

We had a quick walk to the Kashiwanoha park after the lunch. It is located next to the Kashiwanoha campus of the Univ. of Tokyo. The tunnel of full bloom sakura trees are welcoming us and the new season! 

https://indico.in2p3.fr/event/28466/contributions/

The conference, organized by the ILANCE institute from the French Centre National de la Recherche Scientifique (CNRS) at Tokyo University, gathered people from across the globe and from various fields (high energy physics, astroparticles, cosmology, ...). Baptiste presented his work on the measurement of cosmic birefringence and the calibration of polarization angle for future experiment and Clément presented an overview of the LiteBIRD project.

Satsuki  received Master degree in engineering as a graduate studnet in the Ohsaki group at the Univ. of Tokyo. Thanks to her stopping by at IPMU with the beautiful Hakama. We have been collaborating in SMB development for LiteBIRD PMU. Looking forward to continuously working together during your PhD. 

This is for students who made outstanding research during the course of the graduate school of science, the University of Tokyo. He is one of only 4 students selected as this award in the department of physics.

https://www.phys.s.u-tokyo.ac.jp/award/37776/

With the collaborations among Fred, Shunsuke, Asuka, and Tomo, we have received the SO SAT segmented forebaffle. This will be black-painted and shipped to Chile eventually. Baptiste is happy standing next to the hardware!!

Takashi who led various fronts in LiteBIRD over years is leaving the group for the next adventure! Best luck! 

Dr. Bastiste Jost join the Kavli IPMU CMB group. He will lead the SO data analysis. Welcome aboard! 

Ryota (the leftmost) is a graduate student at U. Tokyo, and he has been working with us for several years. His Ph.D. thesis title is a broadband Half-wave Plate for a Space-born 

CMB Polarimeter Using Laser Ablation. The dissertation is submitted to the Department of Physics, Graduate School of Science, The University of Tokyo.

Let's congrats Ryota, now he is Dr. Takaku!

Hideki Tanimura et al. has released the paper about the filaments of the cosmic web shine in the X-rays in the early eROSITA survey data. This work is picked up as the press released from the Kavli IPMU website, [link]. Congratulations! 

Ludo and Baptiste from IRAP, and Thierry from CNES, also Ryota Uematsu and Yuki from Okayama are visiting at Kavli IPMU CMB group. They are looking at the LFT PMU BBM in labB

Guillaume is in a discussion with Alex on the beam simulation using GRASP. Both are visiting IPMU with the CMB-INFLATE program.

Our group members attend the LiteBIRD face-to-face meeting. We presented four posters:

• Teruhito IIDA et al, Preliminary report of development status: cryogenic stepping motor using high purity copper wire

•  Takashi Hasebe et al,  Heat dissipation study for rotation mechanism of polarization modulator unit for LiteBIRDLow-Frequency Telescope

• Hideki Tanimura et al, Cosmology with the Sunyaev Zel’dovich effect for the S8 tension

• Thuong Hoang et al, Preliminary results of the prototype LFT PMU encoder: raw data, analysis, and stability

The Kavli IPMU visitors also presented two posters:

• Alexandre Adler (from Univ. of Stockholms, Sweeden), Determining dimensions for LFT half-wave plate

• Alessandro Novelli (from Università La Sapienza, Italy),  A possible gain calibration approach for the detectors of the LiteBIRD satellite.

The posters are available on the internal LiteBIRD wiki page.

Alex has experience in GRASP simulation. Using GRASP, he conducted physical optics simulation of the diffraction of a plane wave source inside the LiteBIRD Low-Frequency Telescope (LFT) by the telescope’s aperture. 

By measuring the electric field in the plane of the Half-Wave Plate (HWP) lower side, and the integrated intensity within a given radius from the HWP’s center, spillover is the fraction of the total intensity that lies outside that radius. We can see that the diameter of the HWP is the main driver of spillover, while its position is a next-order effect. Raw spillover for the nominal HWP radius (240 mm) is of the order of 1% for that plane wave input.

This work needs further refinements before we can make definitive statements about spillover.

Alex presented a poster at the LiteBIRD face-to-face meeting for this study.

Alessandro Novelli from the Univ. of Rome, La Sapienza, is visiting IPMU with the CMB-inflate program. 

Dr. Ippei Obata join the Kavli IPMU CMB group. Welcome aboard! 

Dr. Joaquin Armijo join the Kavli IPMU CMB group. Welcome aboard! 

Dr. Hedeki Tanimura join the Kavli IPMU CMB group. Welcome aboard! 

Dr. Clement Leloup join the Kavli IPMU CMB group. Welcome aboard! 

We welcome Prof. Eiichiro Komatsu, Dr. Paolo Campeti, Marta Monelli, and Vyoma Muralidhara from Max-Planck Institute for Astrophysics (MPA), Germany.

We did an experimental lab tour. We introduced our research on the polarization modulation unit (PMU), the transition edge sensor (TES), and the anti-reflective (AR) coating.

We thank the CMB-Inflate program for this visit. 

We welcome assoc. Prof. Guillaume Patanchon from AstroParticle and Cosmology (APC) laboratory, France.  His visit is on the framework  of the CMB-INFLATE project. He gave a seminar on CMB systematic effects.

Speaker: Dr. Shunsuke Adachi (Hakubi Center for Advanced Research, Kyoto University)

Dr. Tommaso Ghigna moves to the International Center for Quantum-field Measurement Systems for Studies of the Universe and Particles (QUP)  for a postdoctoral appointment. 

Website: https://www2.kek.jp/qup/en/ 

Akira Endo's webpage: https://terahertz.tudelft.nl/~endo/index.html 

Our group members (Takashi, Tommaso, Ryota) attended to the SPIE Astronomical Telescopes + Instrumentation  2022.

Website:https://spie.org/conferences-and-exhibitions/astronomical-telescopes-and-instrumentation?SSO=1 

We invited Dr. Clara Vérges from the Center for Astrophysics, Harvard to present remotely her recent research on beam calibration and systematics.

Title: Beam calibration and systematics: from BICEP/Keck to future CMB experiments

We welcome 3-internship students: Felicia Xiao from MIT-USA, Kiara Jacob from Mumbai-India, and Junqi Wang from Nanjing-China, to join the group remotely for 2 months: July 1 - August 31.

Briefly scientific goal: 

Currently, there is no CMB experiment that is optimized to probe the circularly polarized component in CMB. All are for a linearly polarized component of CMB to go after inflation. In this program, let's try to design the CMB telescope optimized for the circularly polarized component in CMB, computationally observe, and analyze the data.

The UTRIP program: https://www.s.u-tokyo.ac.jp/en/utrip/ 

Thanks to the CMB-Inflate program, people from Europe starts arriving at Kavli IPMU. So far, Anto from SISSA, Laura Christa Herold,  Eiichiro from MPA, and more are scheduled to visit Kavli IPMU. Looking forward to meeting you in Japan! 

The CMB-Inflate website: https://sites.google.com/view/cmb-inflate 

The in-person workshop is held in Ferrara Italy. Tomotake is invited to talk on scientific challenges expected from future space experiments.

The workshop website: https://www.fe.infn.it/PlanckFutureCMB/ 

We welcome Anto I Lonappan from International School for Advanced Studies (SISSA). He is collaborating closely with Dr. Toshiya Namikawa on the lensing effect for LiteBIRD.

We welcome prof. Eiichiro Komatsu from Max-Planck Institute for Astrophysics, Germany by taking our weekly group meeting in person.

Thesis title: Development of the Polarization Modulation Unit of LiteBIRD Low-Frequency Telescope for exploration of primordial gravitational waves.

Thesis title: Evaluation of the synchronous signal from rotational half-wave plate installed in the CMB polarimeter.

Our group contributed actively in this collaboration paper. 

The title: Probing Cosmic Inflation with the LiteBIRD Cosmic Microwave Background Polarization Survey. [arXiv]

Abstract: LiteBIRD the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. The Japan Aerospace Exploration Agency (JAXA) selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with an expected launch in the late 2020s using JAXA’s H3 rocket. LiteBIRD is planned to orbit the Sun-Earth Lagrangian point L2, where it will map the cosmic microwave background (CMB) polarization over the entire sky for three years, with three telescopes in 15 frequency bands between 34 and 448 GHz, to achieve an unprecedented total sensitivity of 2.2 µK-arcmin, with a typical angular resolution of 0.5◦ at 100 GHz. The primary scientific objective of LiteBIRD is to search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. We provide an overview of the LiteBIRD project, including scientific objectives, mission and system requirements, operation concept, spacecraft and payload module design, expected scientific outcomes, potential design extensions and synergies with other projects. 

A methodology to provide the polarization angle requirements for different sets of detectors, at a given frequency of a CMB polarization experiment, is presented. The uncertainties in the polarization angle of each detector set are related to a given bias on the tensor-to-scalar ratio r parameter. The approach is grounded in using a linear combination of the detector sets to obtain the CMB polarization signal. In addition, assuming that the uncertainties on the polarization angle are in the small angle limit (lower than a few degrees), it is possible to derive analytic expressions to establish the requirements. The methodology also accounts for possible correlations among detectors, that may originate from the optics, wafers, etc. The approach is applied to the LiteBIRD space mission.

 https://arxiv.org/abs/2202.01324 

Dr. K. Komatsu, who obtained his Ph.D. at Kavli IPMU. After that, he moved to Okayama University for a postdoctoral appointment He will move to industrial in February. Best wishes for his new journey!

R. Takaku et al. has published in the journal of Optics Express on November 30, 2021.

Scientists from the Kavli Institute for the Physics and Mathematics of the Universe and the University of Minnesota, Tomotake Matsumura and Shaul Hanany, and their collaborators have made a new type of optical element that will improve the performance of telescopes studying radiation from the Big Bang. 

The result is highlighted on the IPMU website https://www.ipmu.jp/en/20220127-MUSTANG2  

We present a demonstration of the in-flight polarization angle calibration for the JAXA/ISAS second strategic large class mission, LiteBIRD, and estimate its impact on the measurement of the tensor-to-scalar ratio parameter, r, using simulated data. We generate a set of simulated sky maps with CMB and polarized foreground emission, and inject instrumental noise and polarization angle offsets to the 22 (partially overlapping) LiteBIRD frequency channels. Our in-flight angle calibration relies on nulling the EB cross correlation of the polarized signal in each channel. This calibration step has been carried out by two independent groups with a blind analysis, allowing an accuracy of the order of a few arc-minutes to be reached on the estimate of the angle offsets.

https://iopscience.iop.org/article/10.1088/1475-7516/2022/01/039 

Dr. Thuong D. Hoang join the Kavli IPMU CMB group. Welcome aboard! 

Dr. Yuki Sakurai moves to Okayama University for the Assistant Professor position and Dr. Shunsuke Adachi left the Kavli IPMU CMB group. Best wishes for the new journey! 

We fabricated 30 cm diameter low-pass filter made of alumina with broadband anti-reflective sub-wavelength structures (SWS) made with ultra-short pulsed laser ablation. The average transmittance of the filter between 75 and 105 GHz is 98%. The alumina filter has been integrated into MUSTANG2 instrument coupled to the Green Bank Telescope, and data taken with the filter heat sunk to its nominal 40K stage show performance consistent with expectations: a reduction of about 50% in filters-induced optical power load on the 300 mK stage, and in in-band optical loading on the detectors. This is the first report of an alumina filter with SWS ARC deployed with an operating instrument, and the first demonstration of a large area fabrication of SWS with laser ablation. 

https://arxiv.org/abs/2109.15319

String theory generally predict axion-like particles with a broad mass range. If ultralight axion-like particles exist, they could rotate the linear polarization angle of CMB photons. This effect is known as the cosmic birefringence. This paper proposes a novel method to constrain cosmic birefringence effect which is insensitive to systematics from instrumental mis-calibration angle. This method does not use Galactic foregrounds and is much less sensitive to uncertainties in the foreground components than the method previously proposed in the literature. 

Kunimoto, now Dr. K. Komatsu, who has been working with us here at Kavli IPMU, has successfully defended his Ph.D. thesis, "Development of a polarization modulator for the observation of CMB B-modes in search of primordial gravitational waves with LiteBIRD". Now you are Dr. K. Komatsu. Many congratulations! 

Kunimoto Komatsu et al. have written a paper, "Design of a frequency-independent optic axis Pancharatnam-based achromatic half-wave plate", and it is accepted by Journal Astronomical Telescopes, Instruments, and Systems. 

This paper presents a new design of Pancharatnam-based achromatic half-wave plate (AHWP) that completely eliminates the frequency dependence of the effective optic axis orientation, which is a disadvantage of conventional designs used in past CMB polarization experiments. ArXiv Link 

After a long effort and the coordination of IPMU researchers and LiteBIRD members in Europe and the United States, Samantha's cosmic ray paper submitted to JCAP is accepted without any revisions!
The paper discusses a complete end-to-end simulator for the evaluation of cosmic ray effects in the space mission, from the projected radiative environment, to the detectors, readout, and effects on sky data.

 https://arxiv.org/abs/2107.00473

Shunsuke Adachi and Yuki Sakurai have written a paper, "Material survey for millimeter-wave absorber using 3-D printed mold", and it is accepted by Applied Optics. The paper improved the absorption performance of the new millimeter-wave absorber produced with a 3D printing technique. They optimized absorptive materials used in the millimeter-wave absorber. They found that the best material in the 17 materials that they surveyed had a good low reflectance, especially in the low-frequency range. For their evaluation of the optical performance, the Vector-Network-Analyser (VNA) in our lab. was used.  2105.14237

Dr. Namikawa Toshiya has arrived at Kavli IPMU as the project assistant professor. Looking forward to working with you closely! 

Shunsuke Adachi, Tommaso Ghigna, Takashi Hasebe, Shinya Sugiyama, and Ryota Takaku presented their study at the 19th International Workshop on Low Temperature Detectors (LTD19 [link]). Their poster titles are followings:

• S. Adachi,
  "Millimeter-wave absorber using 3-D printed mold for cryogenic application"

• T. Ghigna,
  "Modelling TES non-linearity induced by a rotating HWP in a CMB polarimeter"

• T. Hasebe, "Modeling of Sensitivity of LiteBIRD"

• S. Sugiyama, "Potential extra noise from a continuously rotating HWP using superconducting magnetic bearing for CMB polarimetry"

• R. Takaku, "Evaluation of instrumental polarization of a 200 mm diameter achromatic HWP with anti-reflective structures and impact on TES non-linearity"

Susanna Azzoni has written a paper, A minimal power-spectrum-based moment expansion for CMB B-mode searches, and it is accepted by JCAP. The paper studies the effectiveness to account the spatial variation of the spectral index by using the the power spectrum based moment expansion method. This method is also applied to the publicly available BICEP2/Keck data, and the proposed method recovered the consistent result. arXiv:2011.11575

Dr. Shunsuke Adachi and Dr. Takashi Hasebe join the Kavli IPMU CMB group. Welcome aboard! 

Yurika Hoshino, Ryota Takaku, and Tomotake Matsumura have presented at JSP. Yurika presented the work related to the sapphire half-wave plate systematics, the misalignment of the optical axis and its implication to the CMB experiment. Ryota presented the status of the AR coating development. Tomo has presented various ceramic samples as a candidate for alumina-like filter. 

Dr. Fred T. Matsuda, Dr. Satoru Takakura, and Dr. William Coulton are leaving the group for the next expedition. Best luck! 

We develop broadband anti-reflective structures on hard materials such as sapphire using ulrta-short pulsed laser ablation. This paper shows that the transmittance between 43 - 161 GHz is above 97% for the fabricated sample, which is arguably the largest bandwidths demonstrated in this wavelength range. Link to the article (arXiv)

In this paper we study the effect that a finite knowledge of the bandpass response  has on the reconstruction of CMB data in the presence of bright Galactic emissions. We propagate this effect all the way to the tensor-to-scalar estimation (the famous r value that all cosmologists have been chasing for more than a decade) to define acceptable calibration requirement of the bandpass response to minimize the bias  on the cosmological deliverables. Link to the article.