How are neutrinos detected if they have no charge and very little mass?

Neutrinos themselves are hard to detect. They are observed indirectly when they interact with other particles, knocking them into motion or causing a reaction that produces detectable charged particles.

What was the significance of the 1973 neutrino interaction observed in the Gargamelle experiment?

This event was significant because it showed a different type of neutrino interacting with an electron, which provided crucial information about the weak force and had implications for the discovery of new particles.

What were the main challenges in building the MINERvA detector?

Challenges included efficiently producing and assembling thousands of delicate scintillator bars with embedded fibers, ensuring light-tight and fire-safe optical cables, and precisely aligning hundreds of phototube pixels.

How did the MINERvA project manage its resources and timeline?

MINERvA was efficient by using existing infrastructure like the MINOS detector and neutrino beam. They also managed funding and production by spreading out purchases and establishing multiple assembly sites, though this led to production delays.

What was the main cause of delays in the MINERvA project?

A significant delay occurred when a fraction of the phototube pixels were found to be misaligned with their fibers, requiring individual realigning and re-testing of about 50 out of 500 phototubes, which became the rate-limiting step.

What are the key lessons learned from the MINERvA project?

The speaker emphasized testing everything early and often, as problems often arise unexpectedly. They also highlighted that building such a large scientific instrument requires a collaborative effort involving many different skills and people ('it takes a village').

How does MINERvA contribute to future neutrino experiments like DUNE?

MINERvA helps write the foundational text on neutrino interactions with different nuclei. This knowledge is crucial for the DUNE experiment to accurately interpret the signals they detect and determine the energy and properties of the neutrinos.

MINERvA: I can’t believe we built the whole thing – Public lecture by Dr. Deborah Harris

Fermilab

Science & Technology4 min read45 min video

May 12, 2022|11,073 views|364|45

Fermilab Physics

Save to Pod

Key Moments

TL;DR

Dr. Deborah Harris recounts the ambitious construction of the MINERvA neutrino experiment, highlighting collaboration and overcoming challenges.

Key Insights

MINERvA (Main INjector Experiment to study NEutrino interactions with VArious nuclei) is a neutrino experiment designed to study neutrino interactions with a wide range of materials.

Understanding neutrino interactions is crucial for probing the nucleus and advancing particle physics, much like using a microscope.

The success of large-scale science projects like MINERvA relies heavily on the collaboration of diverse individuals with specialized skills, not just physicists.

The MINERvA experiment ingeniously utilized existing infrastructure and detectors (like MINOS) to maximize efficiency and minimize costs.

Building MINERvA involved intricate logistical planning, international collaboration, and rigorous testing of components, from scintillator extrusion to phototube assembly.

The project faced and overcame significant challenges, including component misalignment and the need for rigorous safety testing, demonstrating resilience and adaptability.

INTRODUCTION TO MINERvA AND NEUTRINO PHYSICS

Dr. Deborah Harris introduces the MINERvA experiment, an acronym for the Main Injector Experiment to study Neutrino interactions with Various nuclei. She begins by emphasizing the critical role of diverse skills and people in "big science." Neutrinos, fundamental particles with almost no mass and zero charge, are created during nuclear fusion (like in the sun) or radioactive decay. Studying them is challenging because they interact rarely. Unlike charged particles that leave tracks by ionizing materials, neutrinos can only be detected indirectly when they interact with other particles, producing detectable charged particles.

HISTORICAL CONTEXT AND THE NEED FOR STUDY

Harris provides historical context, referencing Enrico Fermi's prediction of neutrino existence during radioactive decay studies and the historic 1973 observation of a neutrino interacting with an electron in the Gargamelle experiment. This interaction, demonstrating the weak force, had implications far beyond neutrino physics. Despite these early discoveries, studying neutrino interactions with atomic nuclei is still vital. MINERvA aims to act as a 'digital microscope' to probe the nucleus better by collecting numerous neutrino interactions across a diverse range of materials, including water, helium, carbon, iron, and lead.

THE FUNDING AND DESIGN REVIEW PROCESS

Securing funding for MINERvA involved a rigorous review process with the Department of Energy, requiring demonstration of mission need, a cost and schedule analysis, and a comparison with alternative approaches. Harris highlights MINERvA's efficiency: utilizing an existing neutrino beam built for other experiments (MINOS and NOvA) and incorporating the MINOS detector's capabilities for specific particle detection. This strategy aimed to build the detector quickly to maximize data collection opportunities.

DETECTOR DESIGN AND CONSTRUCTION STRATEGY

The MINERvA detector features a scintillator core for tracking charged particles, surrounded by denser materials like lead and steel to stop specific particles. Crucially, thin sheets of various nuclei (carbon, iron, lead) are interspersed within the detector to allow interactions to be studied on different targets. The design was conceptualized as a 'chewy center with a crunchy shell.' The construction involved assembling modules composed of scintillator strips, optical fibers for light collection, and phototube electronics, all requiring meticulous alignment and integration.

MANUFACTURING AND LOGISTICAL CHALLENGES

The construction phase presented significant logistical hurdles, involving a vast network of universities and collaborators. Large-scale scintillator extrusion and plane assembly occurred at William & Mary and Hampton University. Optical fibers were crucial for light transport, requiring careful manipulation and testing. PMT (photomultiplier tube) boxes were assembled at Tufts and Rutgers, with components often shipped internationally. Materials had to meet stringent flammability requirements for underground deployment, necessitating careful material selection and custom solutions.

ASSEMBLY, TESTING, AND INITIAL DATA COLLECTION

The detector modules were gradually assembled and tested, including crucial "vertical slice" tests to verify read-out systems. Large-scale fabrication of scintillator planes and PMT boxes eventually moved into "mass production mode." Early tests with cosmic rays confirmed the detector's ability to track particles accurately. Ultimately, the detector was installed underground in Fermilab's intense neutrino beam. The first neutrino event was identified shortly after installation, confirmed by synchronized timing with the accelerator, marking a major victory and the culmination of years of effort.

OVERCOMING RATE-LIMITING STEPS AND FINAL REVIEWS

Despite initial optimism and progress, a critical issue emerged: misalignment in a fraction of the phototube pixels required realignment and re-testing, becoming the new rate-limiting step. This was addressed by installing correctly aligned components as others were fixed. The upstream nuclear target regions, containing graphite, iron, and lead, were then installed. The project successfully completed its final review with the Department of Energy, presenting data from millions of neutrino events as proof of their accomplishments.

THE 'TAKE FEWER' LESSON AND FUTURE IMPLICATIONS

The MINERvA experiment served as a critical learning experience, with key takeaways including the importance of testing everything early and often, and the realization that "it takes a village"—a concept encompassing diverse skills and international collaboration. The work done on MINERvA is foundational for future neutrino experiments like DUNE, providing the necessary data and understanding to interpret complex neutrino interactions in larger detectors and further unraveling the mysteries of the universe.

Mentioned in This Episode

●Products

●Software & Apps

●Organizations

●People Referenced

Common Questions

MINERvA stands for the Main Injector Experiment to Study Neutrino interactions. It is a detector designed to act as a 'digital microscope' to study how neutrinos interact with different types of atomic nuclei.

Topics

MINERvA Experiment Nuclear Interactions Detector Construction Scientific Collaboration Physics Research Weak Force Gargamelle Experiment DUNE Experiment

Mentioned in this video

personJorge Morfin

The previous speaker in the Fermilab public lecture series and a former postdoc on the Gargamelle experiment.

organizationJames Madison University

Located in Virginia, this university was where the phototubes mailed from Japan were initially tested before being sent to NJ and Boston for PMT box assembly.

softwareMINERvA

An acronym for the Main Injector Experiment to Study Neutrino interactions. It's a digital microscope designed to collect and study neutrino interactions on a wide range of nuclei.

organizationTufts University

One of the universities responsible for assembling PMT boxes, creating blue-colored boxes for the detector.

organizationUniversity of Guanajuato

MEXICAN institution whose students assisted in the construction of MINERvA modules at Fermilab.

softwareNOvA

Another experiment that used the same neutrino beam that MINERvA was situated in, highlighting efficient use of resources.

organizationRutgers University

One of the universities responsible for assembling PMT boxes, making red-colored boxes for the detector.

softwareMINOS

A previous experiment that utilized the neutrino beam built for it, and whose detector data was shared with MINERvA.

organizationHampton University

Another university that served as a 'scintillator plane factory' for MINERvA, collaborating with William and Mary and renting a warehouse to accommodate production.

personRyder Han

Fermilab staff photographer credited with taking many of the pictures used in the presentation.

personEnrico Fermi

Scientist who calculated the probability of a neutrino hitting a neutron to produce a proton and an electron, laying theoretical groundwork for neutrino detection.

productCadbury Cream Egg

Used as a humorous analogy to describe the detector's design: a chewy scintillator center ('cream') and a crunchy steel/lead shell.

softwareGargamelle

An experiment that first observed neutrinos interacting with electrons, a significant event in particle physics that had implications beyond neutrino interactions.

organizationNational Science Foundation

An organization that was approached for support in building the MINERvA detector. (Mentioned as part of funding sources).